+First of all, I~would like to thank my supervisor, Jaroslav Ne\v{s}et\v{r}il, for
+introducing me to the world of discrete mathematics and gently guiding my attempts
+to explore it with his deep insight. I~am very grateful to all members of the
+Department of Applied Mathematics and of the Institute for Theoretical Computer
+Science for the work environment which was both friendly and highly inspiring.
+I~also send my acknowledgements to the members of the Math department at ETH Z\"urich and of DIMACS
+at the Rutgers University (especially to J\'anos Koml\'os) where I~spent several
+pleasant months working on what finally become a~part of this thesis.
+
+I~also thank to my family for supporting me during the plentiful years of my study,
+to my girlfriend Ani\v{c}ka for lots of patience when I~was caught by my work and
+hardly speaking, to all the polar bears of Kobylisy for their furry presence, and
+finally to our cats Minuta and Dami\'an for their mastership in hiding my
+papers, which has frequently forced me to think of new ways of looking at problems
+when the old ones were impossible to find.
+