@book{9163,
	author = {Polish Academy of Science, Institute of Mathematics and Skupien, Zdzislaw},
	title = {Combinatorics and graph theory; proceedings of the 30th semester held at the Stefan Banach International Mathematical Cetre Warsaw, Sept. 15-Dec. 17, 1987},
	publisher = {Werszawa,},
	year = {1989},
	address = {Borewieki:}
}