Some general documents about graph homomorphisms:
Definitions,
Bibliography,
Open problems.
L. Lovász: Operations with structures, Acta Math.
Hung. 18 (1967), 321-328. pdf
L. Lovász: On the cancellation law among finite relational
structures, Periodica Math. Hung. 18 (1971), 145-156.
pdf
L. Lovász: Direct product in locally finite categories,
Acta Sci. Math. Szeged 23 (1972), 319-322. pdf
R. Appleson, L. Lovász: A characterization of cancellable
k-ary structures, Periodica Math. Hung. 6 (1975),
17-19. pdf
P. Erdős, L. Lovász, J. Spencer: Strong independence of
graphcopy functions, Graph Theory and Related Topics Academic
Press (1979), 165-172. pdf
L. Lovász: The rank of connection matrices and the
dimension of graph algebras Eur. J. Comb. 27 (2006),
962-970. pdf
L. Lovász and B. Szegedy: Limits of dense graph sequences
J. Comb. Theory B 96 (2006), 933-957. pdf
M. Freedman, L. Lovász and A. Schrijver: Reflection
positivity, rank connectivity, and homomorphism of graphs, J. AMS
20 (2007), 37-51.pdf
L. Lovász: Connection matrices, in:Combinatorics,
Complexity, and Chance, A Tribute to Dominic Welsh, (ed. G.
Grimmet and C. McDiarmid) Oxford Univ. Press (2007), 179-190.pdf
L. Lovász and B. Szegedy: Szemerédi's Lemma for the
analyst, J. Geom. and Func. Anal. 17 (2007), 252-270.
pdf
L. Lovász and B. Szegedy: Testing properties of graphs and
functions, pdf
L. Lovász and V.T. Sós: Generalized quasirandom
graphs, J. Comb. Theory B 98 (2008), 146-163. pdf
L. Lovász and A. Schrijver: Graph parameters and semigroup
functions, Europ. J. Comb. 29 (2008), 987-1002. pdf
C. Borgs, J. Chayes, L. Lovász, V.T. Sós, B.
Szegedy and K. Vesztergombi: Graph limits and parameter testing,
STOC 2006, pdf
C. Borgs, J. Chayes, L. Lovász, V.T. Sós and K.
Vesztergombi: Counting graph homomorphisms, in: Topics in
Discrete Mathematics (ed. M. Klazar, J. Kratochvil, M. Loebl, J.
Matousek, R. Thomas, P. Valtr), Springer (2006), 315-371. pdf
L. Lovász and B. Szegedy: Contractors and connectors in
graph algebras, J. Graph Theory 60 (2009), 11-30.pdf
C. Borgs, J. Chayes, L. Lovász, V.T. Sós and K.
Vesztergombi: Convergent Sequences of Dense Graphs I: Subgraph
Frequencies, Metric Properties and Testing, Advances in Math.
219 (2008), 1801-1851. pdf
C. Borgs, J. Chayes, L. Lovász, V.T. Sós and K.
Vesztergombi: Convergent Sequences of Dense Graphs II: Multiway Cuts
and Statistical Physics, pdf
C. Borgs, J. Chayes and L. Lovász: Moments of Two-Variable
Functions and the Uniqueness of Graph Limits, Geom. Func.
Anal. 19 (2010), 1597-1619.pdf
L. Lovász and A. Schrijver: Dual graph homomorphism
functions, J. Comb. Theory A 117, 216-222. pdf
L. Lovász and A. Schrijver: Semidefinite functions on
categories, Electron. J. Combin. 16 (2009), no. 2,
Special volume in honor of Anders Björner, Research Paper 14, 16 pp.
pdf
L. Lovász: Very large graphs, Current Developments in
Mathematics 2008 (eds. D. Jerison, B. Mazur, T. Mrowka, W.
Schmid, R. Stanley, and S. T. Yau), International Press, Somerville,
MA (2009), 67-128. pdf
L. Lovász and B. Szegedy: Finitely forcible graphons,
pdf
C. Borgs, J. Chayes, L. Lovász, V.T. Sós and K.
Vesztergombi: Limits of randomly grown graph sequences, pdf
L. Lovász and B. Szegedy: Random Graphons and a Weak
Positivstellensatz for Graphs, pdf
L. Lovász and B. Szegedy: Regularity partitions and the
topology of graphons, pdf
C. Borgs, J. Chayes, J. Kahn, L. Lovász: Left and right
convergence of graphs with bounded degree pdf
L. Lovász: Subgraph densities in signed graphons and the
local Sidorenko conjecture, pdf
L. Lovász and B. Szegedy: The graph theoretic moment
problem pdf
L. Lovász and B. Szegedy: Limits of compact decorated
graphs pdf
Jan Draisma, Dion Gijswijt, László Lovász, Guus Regts, Alexander
Schrijver: Characterizing partition functions of the vertex model,
pdf