1. Endomorphism spectra of graphs;Böttcher;Discrete Mathematics,1992
2. Semigroups, Theory and Application. Proceedings Oberwolfach 1986;Fleischer,1988
3. Wreath products of monoids with small categories whose principal one-sided ideals form tress;Fleischer;Journal of Algebra,1994
4. Graph homomorphisms: structure and symmetry;Hahn,1997
5. Product graphs; structure and recognition;Imrich,2000