A J(4) system is a family ~9 of k distinct sets which have pairwise the same intersection A weak 3 (k ) system is a family 9 of k distinct sets such that j b n G i = t for some non-negative integer Iâ€¦ (More)

A star forest of a graph G is a spanning subgraph of G in which each component is a star. The minimum number of edges required to guarantee that an arbitrary graph, or a bipartite graph, has a starâ€¦ (More)

Let G be a simple graph on n vertices with list chromatic number Ï‡l = s. If each vertex of G is assigned a list of t colours Albertson, Grossman and Haas [1] asked how many of the vertices, Î» t,s,â€¦ (More)