CV/Professional Life
Education
 Ph.D., Department of Mathematics, University of Pennsylvania, Philadelphia, USA, 1987
Thesis: “Some Extremal Problems for Graphs with Fixed Numbers of Vertices and Edges,”
Advisor: Professor H.S. Wilf
 M.S. (Diploma), Mathematics, Kiev State University, Kiev, USSR, 1975
Thesis: “Arrangements of Some Geometrical Groups in Symmetric Groups”
Advisors: Professors L.A. Kaluznin and M.H. Klin
Research Interests
Combinatorics, Graph Theory, Algebra, Geometry.
I am interested in other topics and willing to work on any problem I like.
Service Outside the Department
I am a member of the Editorial Board of the Electronic Journal of Combinatorics .
Employment
 Visiting Professor, University of Pennsylvania, Spring, 2001 (sabbatical)
 Visiting Researcher, DIMACS, Rutgers University, Fall 2000 (sabbatical)
 Professor, Department of Mathematical Sciences, University of Delaware, since 9/1998
 Associate Professor, Department of Mathematical Sciences, University of Delaware, 9/19938/1998
 Visiting Researcher, RUTCOR, Rutgers University, 912/ 1993 (sabbatical)
 Assistant Professor, Mathematical Sciences, University of Delaware, 9/19878/1993
 Lecturer (part time), Haverford College, Spring 1987
 Lecturer and TA , University of Pennsylvania, 9/19805/1987
 Lecturer (part time), Spring Garden College of Philadelphia, 19841986
 Lecturer (part time), Philadelphia Community College, 19811982
 Actuarial Assistant, General Accident Ins.Co., 2/19827/1983
 Teacher of Mathematics, Dynamic Springs Private School, Media, PA, Summer 1988
 Teacher of Mathematics, Mathematics and Physics Boarding High School at Kiev State University, Kiev, USSR, 1975–1979
Research Advising

 Dr. Vladislav Taranchuk (Ph.D. — 5/2023).
 Dr. Melissa Fuentes (Ph.D. — 5/2021), Villanova University, PA.
 Dr. Benjamin Nassau (Ph.D. — 8/2020), Rowan University, NJ.
 Dr. Lorinda Leshock (Ph.D. — 8/2020), Data Scientist, R&D West Pharmaceutical Services, Exton, PA.
 Dr. Shuying Sun (Ph.D. — 5/2017, coadvised with Dr. N. Bhatnagar). Microsoft, Seattle, WA.
 Dr. James Alexander (Ph.D. — 5/2016), Synopsys Inc., Mountain View, CA.
 Dr. Ye Wang (8/2013 — 8/2014, visiting graduate student from Tongji University, China. Ph.D. — 2015). Harbin Engineering University, China.
 Dr. Alexandr Kodess (Ph.D. — 8/2014), Farmingdale State College, NY.
 Dr. Brian Kronenthal (Ph.D. — 5/2013), Kutztown University, Kutztown, Pennsylvania.
 Dr. Bryan Petrak (Ph.D. — 6/2012, coadvised with Dr. G.L. Ebert). Boeing Corp., Oklahoma City, Oklahoma.
 M.A. Thesis advisor for Dr. Spencer Tofts (20102011), Ph.D. from the University of Pennsylvania in 2016. Google, Pittsburg, PA.
 Undergraduate Research Program for Dr. Michael Tait (Summer, Fall 2009). Ph.D. in Mathematics from UC San Diego.
 Dr. Bill Cuckler (9/2006 — 9/2008), post doctoral student. DOD.
 Undergraduate Research Program for Dr. Alison Gordon Lynch (Summer 2006). Ph.D. in Mathematics from University of Wisconsin.
 Undergraduate Research Program for Robert DeMarco (Summer 2005 — Spring 2006). Ph.D. in Mathematics from Rutgers University.
 Dr. Jason Williford (Ph.D. — 6/2004), University of Wyoming, Laramie, Wyoming.
 Dr. Vasyl Dmytrenko (Ph.D. — 6/2004), Temple University, Philadelphia, PA. 1961 — 2013.
 Dr. Sven Reichard (Ph. D. — 6/2003, (coadvised with Dr. M.H. Klin).
 Dr. Raymond Viglione (Ph.D. — 6/2002 ), Kean University, Union, New Jersey.
 Undergraduate Research Program and Honor Thesis (coadvised with Dr. G.L. Ebert) for David Kravitz (graduated in 5/2000).
Ph.D. from CarnegieMellon University.
 Dr. Owen Byer (Ph.D. — 5/1996 ), Eastern Mennonite University, Harrisonburg, Virginia.
 Undergraduate Research Program and Honor Thesis (coadvised with Dr. W. Li) for Ryan Martin (graduated in 5/1995). Ph.D. from Rutgers University.
Dr. Ryan Martin, Iowa State University, Ames, Iowa.
 M.S. Thesis advisor for Alexander Schliep (graduated in 2/1994 ). Ph.D. from Max Plank Institute.
Dr. Alexander Schliep , Chalmers — Gothenburg University.
 Dr. Gene Fiorini , (Ph.D. — 6/1993), DIMACS, Rutgers University, Piscataway, New Jersey.
 Undergraduate Research Program for Samuel Stump (Summer 1992).
Teaching
University of Delaware:
Undergraduate Courses:
 Discrete Mathematics I (M210)
 Calculus with Applications (M221)
 Finite Mathematics with Applications (M230)
 Calculus I (M241), Calculus II (M242 – with Maple)
 Calculus III (M243 – in Computer Classroom with Maple)
 ODE with Applications (M302 in Computer Classroom with Maple)
 Discrete Mathematics II (M315)
 History Of Mathematical Ideas (M308)
 Linear Algebra (M349)
 Graph Theory (M389)
 Abstract Algebra (M450/M451)
 Ideas of Geometry (Summer College, Special Programs)
 Geometry (M540)
 Geometry (a special summer course for DPI Critical Curriculum Program)
 Discrete Mathematics (a special summer course for DPI Critical Curriculum Program)
 Coding Theory (M567)
Graduate Courses:
 Foundations of Mathematics I, II (M567) (for Ph.D. Program in Mathematics Education)
 Abstract Algebra (M650)
 Vector Spaces (M672)
 Combinatorics I (M688)
 Combinatorics II (M689)
 Methods of Linear Algebra in Combinatorics (Thematic Seminar – M699)
 Group Theory with Applications (M845)
 Field Theory with Applications (M846)
 Asymptotic Theory of Designs (Topic Course – M867)
 Extremal Combinatorics (M885)
Reading Courses:

 Selected topics in Abstract Algebra (three different courses)
 Finite NonDesaguesian planes
 Finite Fields
 Finite Geometries
 Methods of Linear Algebra in Graph Theory
 Algebraic methods in Combinatorics
 Topics in Combinatorics and Graph Theory (five different cources)
 Extremal Graph Theory
 Probabilistic Methods in Combinatorics and Graph Theory
 Nowherezero flows in graphs
University of Pennsylvania


Algebra and Functions; Ideas of Mathematics and Computer; Introduction to Mathematics II; Calculus I, II, III; Advanced Calculus; Linear Algebra; Summer Enrichment Program for Gifted Children (3 different courses)
as Teaching Assistant:


Calculus I – Computer Section (Fortran), Calculus I, II – Computer Sections (Basic) Real Analysis; Ordinary Differential Equations
Haverford College:


Problem Solving in Pascal
Spring Garden College of Philadelphia:



Precalculus I, II; Calculus I, II
Philadelphia Community College:

Basic Arithmetic I, II; Basic Algebra and Mathematical Concepts
Math – Physics Boarding High School at the Kiev State University:

Three year special course in mathematics (included regular and advanced topics of the highschool curriculum in algebra, geometry and calculus; number theory; abstract algebra; geometric transformations; preparation of the school teams for mathematical olympiads.
Invited Talks at Conferences
 DIMACS Workshop on Expanding Graphs and Applications, Princeton University, Princeton, NJ, May 11–14, 1992.
 AMS meeting, Special Section on Extremal Combinatorics and Graph Theory, DeKalb, IL, May 1993.
 The International Conference “Algebra and Combinatorics: Interactions and Applications”, Konigstein, Germany, March 1994.
 The 6–th International Conference on Formal Power Series and Algebraic Combinatorics, Rutgers University, New Brunswick, NJ, May 1994.
 The The NSF/CBMS Research Conference on Eigenvalues and Combinatorics, CSU, Fresno, CA, June 1994.
 Invited Speaker at the award ceremony for The Delaware Mathematical League, Dover, DE, March 1995.
 A Combinatorics and Graph Theory Conference in Honor of Herb Wilf’s 65th birthday, University of Pennsylvania, Philadelphia, Pa, June 1996.
 Workshop on Extremal Combinatorics, Mathematical Sciences Research Institute, Berkeley, November 1996.
 International Colloquium on Extremal Graph Theory, dedicated to the memory of Paul Erdos, Balatonlelle, Hungary, July 1997.
 AMS meeting, Special Section on Combinatorics and Graph Theory, Louisville, Kentucky, March 1998.
 DIMACS Research & Education Institute 1998: Graph Theory and Combinatorial Optimization, DIMACS Center, Rutgers University, Piscataway, NJ, July, 1998.
 First Annual K12 MegaConference on Discrete Mathematics, DIMACS Discrete Math/Theory of Computing Seminar, DIMACS Center, Rutgers University, Piscataway, NJ, December, 1998 (two 2.5 hour workshops for high school teachers).
 Joint CMSAMS meeting, Special Section on Extremal Combinatorics and Graph Theory, Queen’s University, Kingston, Canada, December, 1998.
 AMS meeting, Special Section on Combinatorics and Graph Theory, SUNY, Buffalo, New York, April 1999.
 DIMACS Mathematics Series, AT & T, Shannon Laboratory, Florham Park, NJ, October 2000.
 AMS meeting, Special Section on Extremal Combinatorics, University of Indiana, Bloomington, Indiana, April 2003.
 AMS meeting, Special Section on Finite Geometries, University of Colorado, Boulder, Colorado, October, 2003.
 AMS meeting, Special Section on Extremal Combinatorics, Vanderbilt University, Nashville, Tennessee, June, 2004.
 AMS meeting, Special Section on Extremal Combinatorics, Northwestern University, Evanston, Illinois, October 2004.
 WaterMellon Workshop on Extremal Graph Theory, Carnegie Mellon University, Pittsburgh, Pennsylvania, May, 2005.
 AMS meeting, Special Section on Extremal and Probabilistic Combinatorics, University of Arkansas, Fayetteville, Arkansas, November, 2006.
 EXCILL: Extremal Combinatorics at Illinois, University of Illinois, UrbanaChampaign, Illinois, November, 2006.
 AMS meeting, Special Section on Algebraic and Extremal Combinatorics, Davidson College, North Caroline, March 2007.
 Workshop on Extremal Combinatorics, Alfred Renyi Institute of Mathematics, Budapest, Hungary, June 2007.
 WaterMellon Workshop on Extremal Graph Theory II, University of Waterloo, Canada, June, 2009.
 Rocky Mountain Discrete Mathematics Day, University of Colorado at Denver, Denver, Colorado, June, 2009.
 AMS Central Section meeting, Special Section on Extremal and Probabilistic Combinatorics, Macalester College, St Paul, Minnesota; April 2010.
 Spring 2010 AMS Eastern Sectional meeting, Special Section on Graph Theory, NJIT, Newark, New Jersey; May 2010.
 Workshop on Linear Algebra Techniques in Combinatorics and Graph Theory, Banff International Research Station, Banff, Alberta, Canada; JanuaryFebruary 2011.
 Rocky Mountain Discrete Mathematics Day, University of Wyoming, Laramie, Wyoming; June 2013.
 The 6th International Workshop on Optimal Network Topologies, Bratislava, Slovakia; JuneJuly 2014.
 28th Cumberland Conference on Combinatorics, Graph Theory and Computing University of South Carolina, Columbia, SC; May 2015;
 The Third Annual Conference for the Exchange of Mathematical Ideas, Department of Mathematics, University of Mary Washington, Fredericksburg, VA, USA; June 2015.
 Discrete Mathematics Days 2016, The Fields Institute for Research in Mathematical Sciences, Carleton University, Ottawa, Canada; May 2016
 The 7th International Workshop on Optimal Network Topologies, Tsinghua Sanya International Mathematics Forum, Sanya, China. July 2016.
 Fall Western Sectional Meeting of the AMS, Special Section on Algebraic Combinatorics, University of Denver, Denver, Colorado; October 2016.
 Conference on Algebraic and Extremal Graph Theory (AEGT), University of Delaware, Delaware; August, 2017. The conference photograph is: here.
 CanaDAM 2019, Special Minisymposium on Extremal Combinatorics, Simon Fraser University, Vancouver, Canada; May 2019.
 Workshop on Extremal Graphs arising from Designs and Configurations, Banff International Research Station, Banff, Alberta, Canada; May 2023.
 International Workshop on Optimal Network Topologies, ICMS, Bayes Centre, Edinburgh, UK; July 2023.
Other conferences, contributed talks, colloquia, seminars, lectures, professional visits
 Two talks at Mathematical Colloquium in University of Kiev, 1974–1975.
 Two talks at the Kiev High School Teachers Seminar, Kiev, 1977.
 AMS Meeting, Fairfield, CT, October, 1983.
 ICM86, Berkeley, CA, August, 1986.
 Lecture for High School Students: “Why Math?”, April 1986.
 Four Lecture Seminar for Elementary School Teachers, Abington, PA, October 1987.
 Conference on Probabilistic Methods in Combinatorial Optimization, Baltimore, MD, June 1987.
 RUTCOR Conference, Newark, NJ, November, 1987.
 AMS–MAA Meeting, Atlanta, GA, January, 1988; contributed talk.
 Nineteenth Southeastern International Conference on Combinatorics, Graph Theory and Computing, LSU, Baton Rouge, LA, February, 1988; contributed talk.
 Third Advanced Research Institute on Discrete Applied Mathematics, RUTCOR, New Brunswick, NJ, May, 1988.
 Lecture for general public: “What is Mathematics?”, October 1988.
 Sixth International Conference on Graph Theory and Applications, Western Michigan University, Kalamazoo, MI, June, 1988; contributed talk.
 AMS–MAA Meeting, Phoenix, AZ, January, 1989
 Twentieth Southeastern International Conference on Combinatorics Graph Theory, Computing, FAU, Boca Raton, FL, February, 1989; contributed talk.
 A talk at the Combinatorics Seminar at George Washington University, Washington, D.C., April, 1989
 The Capital City Conference on Combinatorics and Theoretical Computer Science, The George Washington University, Washington, D.C., May, 1989; contributed talk.
 The Fourth Advanced Research Institute on Discrete Applied Mathematics, RUTCOR, New Brunswick, NJ, June, 1989; contributed talk.
 Joint Summer Research Conference on Probabilistic and Analytic Methods in Discrete Mathematics, Humbolt State University, Arcata, CA, June, 1989.
 AMS–MAA Meeting, Louisville, KY, January, 1990.
 Twenty–first Southeastern International Conference on Combinatorics, Graph Theory and Computing, FAU, Boca Raton, FL, February 1990.
 A talk at the Combinatorics Seminar at George Washington University, Washington, D.C., March 1990.
 Fifth Advanced Research Institute on Discrete Applied Mathematics, RUTCOR, New Brunswick, NJ, May, 1990; contributed talk.
 Fifth SIAM Conference on Discrete Mathematics, Atlanta, GA, August 1990; Organized (with other members of Combinatorics/Algebra Group, UD) and chaired a mini symposium on “Irregular Networks”, which took place during the conference.
 ICM–90, Kyoto, Japan, August 1990; contributed talk.
 AMS–MAA Meeting, San Francisco, CA, January 1991. Attended a two day mini course on “Probabilistic Methods in Combinatorics”, which took place before the meeting
 Winter Meeting of the EPADEL Section of the MAA, U.D., Newark, DE, January, 1991.
 Twenty–second Southeastern International Conference on Combinatorics, Graph Theory and Computing, LSU, Baton Rouge, LA, February 1991; contributed talk.
 Sixth Advanced Research Institute on Discrete Applied Mathematics, RUTCOR, New Brunswick, NJ, June, 1991; contributed talk.
 Fall Meeting of the EPADEL Section of the MAA, Drexel University, Philadelphia, PA, November, 1991.
 Twenty–third Southeastern International Conference on Combinatorics, Graph Theory and Computing, FAU, Boca Raton, FL, February 1992; contributed talk.
 Colloquium Speaker at the Department of Mathematics, George Washington University, Washington, D.C., April 1992.
 Seventh Advanced Research Institute on Discrete Applied Mathematics, RUTCOR, New Brunswick, NJ, May–June, 1992; contributed talk.
 Seventh International Conference on Graph Theory and Applications, Western Michigan University , Kalamazoo, MI, June, 1992; contributed talk.
 Sixth SIAM Conference on Discrete Mathematics, University of British Columbia, Vancouver, Canada, June, 1992; contributed talk.
 A talk at the Temple Number Theory/Combinatorics/Modular Forms Seminar, Temple University, Philadelphia, November 4, 1992.
 Holiday Symposium on Lie Group Representations and Combinatorics, Las Cruses, New Mexico, December 1992; contributed talk.
 1993 SIAM Annual Meeting, Philadelphia, June 1993; chaired a session on Combinatorics and Graph Theory; contributed talk.
 The International Conference on Combinatorics, Paul Erd\H os is Eighty, International Conference sponsored by Janos Bolyai Mathematical Society, Keszthely, Hungary, July 1993; contributed talk.
 A talk at the Combinatorics Seminar at George Washington University, Washington, D.C., December 1993.
 Colloquium Speaker, RUTCOR, Rutgers University, December 1993.
 The Seventh SIAM Conference on Discrete Mathematics, Albuquerque, NM, June 1994; contributed talk.
 Math 301: Implementation of Standards, Teacher’s conference, Ocean City, MD, November, 1994
 Eight Cumberland Conference on Graph Theory, Combinatorics and Computing, Vanderbilt University, Nashville, TN, April 1995; contributed talk.
 The 15–th British International Conference on Combinatorics, University of Stirling, Stirling, Scotland, July 1995; contributed talk.
 Colloquium Speaker, Gettysburg College, Gettysburg, PA, October 1995
 Twenty–Seventh Southeastern International Conference on Combinatorics, Graph Theory and Computing, LSU, Baton Rouge, LA, February 1996; contributed talk.
 Colloquium Speaker, Shippensburg University, Shippensburg, PA, March 1996.
 Eighth International Conference on Graph Theory, Combinatorics, Algorithms and Applications, Western Michigan University , Kalamazoo, MI, June, 1996; contributed talk.
 A talk at Combinatorics Seminar, Department of Mathematics, Tel Aviv University, Tel Aviv, Israel; January 1997.
 A talk at a joint meeting of Combinatorics Seminar and The Amitsur Algebra Seminar, Department of Mathematics, Hebrew University, Jerusalem, Israel; January 1997.
 A talk at Algebra Seminar, Department of Mathematics, Center for Teaching and Technology, Holon, Israel; January 1997.
 A talk at the Combinatorics Seminar, Department of Mathematics, Technion, Haifa, Israel; January 1997.
 A talk at Algebra Seminar, Department of Mathematics and Computer Sciences, BarIlan University, BarIlan, Israel; January 1997.
 Colloquium Speaker, Department of Mathematics and Computer Science, BenGurion University, BeerSheva, Israel; January 1997.
 TwentyEigth Southeastern International Conference on Combinatorics, Graph Theory, Computing, FAU, Boca Raton, FL, February 1997; contributed talk.
 A talk at DIMACS Discrete Math/Theory of Computing Seminar, DIMACS Center, Rutgers University, Piscataway, NJ, February 1997.
 Colloquium Speaker, Department of Mathematics, Emory University, Atlanta, Georgia; April 1997.
 The 16–th British International Conference on Combinatorics, Queen Mary and Westfield College, London, July 1997; contributed talk.
 Fall Meeting of the EPADEL Section of the MAA, University of Pennsylvania, Philadelphia, PA, November 1997.
 TwentyNinth Southeastern International Conference on Combinatorics, Graph Theory, Computing, FAU, Boca Raton, FL, March 1998; contributed talk.
 TwentyThird Australian Conference on Combinatorial Mathematics and Combinatorial Computing, University of Queensland, Brisbane, Australia; July 1998; contributed talk.
 A talk at Number Theory/Cryptology Seminar, Department of Mathematics and Computer Sciences, Macquiry University, Sydney, Australia; July 1998.
 A talk at Faculty/Student Seminar, Messiah College, Grantham, PA; December 1998.
 Colloquium Speaker, Department of Mathematics, Lehigh University, Bethlehem, PA; December 1998.
 KCC99 (a Combinatorics Conference in Honor of D. Kleitman’s 65th birthday), Department of Mathematics, MIT, Cambridge, MA; August 1999.
 A talk at Discrete Mathematics Seminar, Department of Mathematics, Princeton University, NJ; March 2000.
 The Ninth Quadrennial International Conference on Graph Theory, Combinatorics, Algorithms and Applications, June 49, 2000, Kalamazoo, MI, USA; contributed talk.
 The 6th International Conference on Graph Theory, August 28September 1, 2000, Marseille, France; contributed talk.
 A talk at Discrete Mathematic Seminar, University of Memphis, Memphis, TN, October, 2000. (A five day visit.)
 Colloquium Speaker, Department of Mathematics, US Naval Academy, Annapolis, MD; April, 2001.
 A talk at Combinatorics Seminar, Cambridge University, Cambridge, UK, May, 2001. (A two week visit.)
 A talk at Discrete Mathematics Seminar, Department of Mathematics, Princeton University, NJ; December 2001.
 Colloquium Speaker, Department of Mathematics, Drexel University, Philadelphia, PA; January, 2002.
 ThirtyThird Southeastern International Conference on Combinatorics, Graph Theory, Computing, FAU, Boca Raton, FL, March 2002; contributed talk.
 A talk at Combinatorics Seminar, Microsoft Research Theory Group, Redmont, WA, MayJuly, 2002. (One and two week visits.)
 MidAtlantic Center for Mathematics Teaching and Learning Conference, Pennsylvania State University, State College, PA, June 2002.
 Geometric and Algebraic Combinatorics 2, Oisterwijk, the Netherlands, August 1116, 2002; contributed talk.
 A talk at Discrete Mathematics Seminar, Department of Mathematics, Princeton University, NJ; April 2003.
 Extremal Combinatorics, Conference and Workshop, Renyi Institute of Mathematics, Budapest/Czopak, Hungary, JuneJuly, 2003; contributed talks.
 Combinatorics in Cambridge (celebrating Bela Bollobas’s 60th birthday), Cambridge UK, August 47, 2003.
 Organized (with David Fleshner) an EPADEL Conference for Undergraduates “Careers in Mathematics”, Gettysbyrg College, Gettysburg, PA; November 2003.
 A talk at Combinatorics Seminar, Department of Mathematics, University of Illinois at Chicago, IL; December 2003.
 A talk for the Mathematics Awarness Week at the University of Delaware, Newark, Delaware, April, 2004.
 A talk at Combinatorics Seminar, Department of Mathematics, University of Pennsylvania, Philadelphia, PA; December 2004.
 Colloquium Speaker, Department of Mathematics, Iowa State University, Aimes, Iowa; January, 2005.
 AMS Meeting, Special Section on Coding and Finite Geometries. University of Delaware, Newark, Delaware; April 2005.
 A talk at Tutte Seminar, Department of Combinatorics and Optimization, University of Waterloo, Waterloo, Canada; April 2005.
 AMS Meeting, Special Section on Extremal and Probabilistic Combinatorics. Bard College, AnnandaleonHudson, New Yourk, USA; October 2005.
 Lie Groups, Representations and Discrete Mathematics Workshop, IAS, Princeton, New Jersey, USA; February 2006.
 Department of Combinatorics and Optimization, University of Waterloo, Waterloo, Canada; March 2006. (A five day visit.)
 A talk at Combinatorics Seminar, Department of Mathematics, University of Pennsylvania, Philadelphia, PA; April 2006.
 SIAM Conference on Discrete Mathematics, University of Victoria, Victoria, British Columbia, Canada; June 2006 (Coorganizer of minisimposium; contributed talk.)
 Colloquium Speaker, Department of Mathematics, US Naval Academy, Annapolis, MD; October, 2006.
 A talk at the Combinatorics Seminar at George Washington University, Washington, D.C.; October 2006.
 AMS meeting, Special Section on Finite Geometries, Miami University, Oxford, Ohio, March 2007.
 A talk at the Combinatorics/Geometry Seminar, Department of Mathematics, University of Colorado at Denver, Denver, Colorado, April 2007. (A four day visit.)
 Colloquium Speaker, Department of Mathematics, University of Mary Washington, Fredericksburg, VA; October, 2007.
 Colloquium Speaker, Department of Mathematics, University of Miami, Oxford, OH; October, 2007.
 Additive Combinatorics Workshop, IAS, Princeton, NJ; OctoberDecember 2007.
 Expanders in Pure and Applied Mathematics, IPAM, UCLA, CA; February 2008.
 A talk at the Combinatorics Seminar, Department of Mathematics, UCSD, La Jolla, CA; March 2008. (A two week visit.)
 A talk at the Combinatorics Seminar, Department of Mathematics, LSE, London, UK; May 2008. (A four day visit.)
 A talk at the Combinatorics Seminar, Department of Mathematics, University of Cambridge, UK; May 2008. (A week visit.)
 A lecture for high school students, Liceum #38, Kiev, Ukraine; May 2008.
 A talk at the Geometry Seminar, Department of Mathematics, University of Ghent, Ghent, Belgium; June 2008. (A two week visit.)
 Colloquium Speaker, Department of Mathematics, University of Liege, Belgium; June 2008.
 The 9th International Conference on Finite Fields and Their Applications, University College Dublin, Ireland, July 2009; contributed talk.
 Workshop on Exremal and Probabilistic Combinatorics, IPAM UCLA, CA; November 2009.
 International Conference on Designs, Codes and Geometries in Honor of Gary Ebert on the occasion of his retirement,
University of Delaware, Lewis, Delaware; March–April 2010. (Coorganized the conference with Qing Xiang.)
 From A=B to Z=60. Conference in Honor of Doron Zeilberger’s 60th Birsday, DIMACS, Piscataway, NJ; May, 2010.
 A talk at the Combinatorics Seminar, Department of Mathematical Sciences, Carnegie Mellon University, Pittsburgh, PA.; November 2010.
 Department of Combinatorics and Optimization, University of Waterloo, Waterloo, Ontario, Canada; May 2011. (A two day visit.)
 Waterloo Workshop in Computer Algebra 2011, W80, Wilfried Laurier University, Waterloo, Ontario, Canada; May 2011.
 A talk at the Discrete Mathematics Seminar, Department of Mathematics, University of Wyoming, Laramie, Wyoming; July 2011 (a week visit).
 Colloquium Speaker, Department of Mathematics, Howard University, Washington, DC; November, 2011.
 Rocky Mountain Discrete Mathematics Day, University of Colorado at Fort Collins, Fort Collins, Colorado, May 2012; contributed talk.
 Department of Mathematics, University of Wyoming, Laramie, Wyoming; May 2012 (a four day visit).
 Department of Mathematics, UCSD, La Jolla, CA; August 2012 (a week visit.)
 Midwestern Graph Theory (MIGHTY) LIII Conference, Iowa State University, Ames, Iowa, September 2012; contributed talk.
 Alumni reunion/Pi Mu Epsilon induction ceremony, Saint Joseph’s University, April 2013; a fifty minute lecture.
 The Twenty Fourth British International Conference on Combinatorics, Royal Holloway, University of London, July 2013, UK; contributed talk.
 A talk at the Experimental Mathematics Seminar, Rutgers University, Piscataway, NJ; October 2013.
 Colloquium Speaker, Department of Mathematical Sciences, Michigan Technological University, Houghton, Michigan; October 2013 (a week visit).
 AMS meeting, Special Section on Algebraic Methods in Graph Theory and Combinatorics, University of Tennessee, Knoxville, TN, March 2014 (session coorganizer).
 An International Conference on Modern Trends in Algebraic Graph Theory, Villanova University, Villanova, Pennsylvania, June 2014.
 Workshop on Probabilistic and Extremal Combinatorics, Institute for Mathematics and its Applications, University of Minnesota in Minneapolis, MN, September 2014 (a week visit).
 A talk at the Combinatorics Seminar, Department of Mathematics, Polytechnic University of Catalonia, Barcelona, Spain, October 2014 (a two week visit).
 A talk at the Combinatorics Seminar, Department of Mathematics, University of Warwick, UK; October 2014 (a week visit).
 A talk at the Combinatorics Seminar, Department of Mathematics, University of Cambridge, UK; October 2014 (a week visit).
 A talk at the Combinatorics Seminar, Department of Mathematics, UCSD, La Jolla, CA; March 2015 (a week visit).
 The 12th International Conference on Finite Fields and Their Applications, Skidmore College, Saratoga, NY, July 2015; contributed talk.
 Combinatorics: Challenges and Applications, Celebrating Noga Alon’s 60th Birthday, January, 2016, Tel Aviv University, Tel Aviv, Israel.
 A talk at the Finite Fields and Combinatorics Seminar, Institute of Information Engineering of the Chinese Academy of Sciences, Beijing, China; June 2016 (a three day visit).
 A talk at the Combinatorics Seminar, Department of Mathematics, Beijing University, China; July 2016 (a four day visit).
 Department of Mathematics, Zhejiang University, Hongzhou, China; July 2016 (a three day visit).
 Department of Mathematics, Tongji University, Shanghai, China; July 2016 (a five day visit).
 Colloquium Speaker, Gettysburg College, Gettysburg, PA, April 2017.
 Colloquium Speaker, University of South Florida, Tampa, FL, April 2017.
 Colloquium and REU program Speaker, Lafayette College, Easton, PA, June 2017.
 The Second Malta Conference in Graph Theory and Combinatorics, Qawra, Malta, June 2017; contributed talk.
 A talk at the Discrete Mathematics Seminar, Virginia Commonwealth University, Richmond, VA, January, 2018.
 A talk at the Discrete Mathematics Seminar, George Washington University, Washington, DC, April, 2018.
 Building Bridges II. Conference to celebrate 70th birthday of Laszlo Lovasz. Budapest, Hungary, July 2018.
 Coorganized (with S. Cioaba, B. Kronenthal, and T. Wong) a Special Section of the AMS meeting on Graph Theory and Applications, University of Delaware, Newark, Delaware, September 2018.
 A talk at the Combinatorics Seminar, Iowa State University, Ames, Iowa, April 2019.
 Conference dedicated to the 25th Anniversary of the Electronic Journal of Combinatorics, CanaDAM 2109, Simon Fraser University, Vancouver, Canada; May 2019.
 Fq14: Conference on Finite Fields and their applications, Simon Fraser University, Vancouver, Canada; June 2019; contributed talk.
 A talk at the Teaching Seminar, University of Delaware, May 2021.
 A talk at the Mirka Miller’s Combinatorics Webinar Series, June 2021.
 A talk at the Combinatorics Seminar, University of Wyoming, Laramie, WY, November 2021.
 A talk at the Teaching Seminar, University of Delaware, November 2021.
 A sequence of three talks: In Elliptic World I, II, III, University of Delaware, December 2021, March 2022.
 The 15th Annual Thomas L. Pirnot Lecture in Mathematics, Kutztown University of Pennsylvania, April, 2022.
Societies
 American Mathematical Society (AMS)
 Fellow of the Institute of Combinatorics and its Applications