1. On the complexity of H-coloring;Hell;J. Comb. Theory Ser. B,1990
2. The effect of two cycles on the complexity of colorings by directed graphs;Bang-Jensen;Discrete Applied Math.,1990
3. The complexity of coloring by semicomplete digraphs;Bang-Jensen;SIAM J. Math.,1988
4. On the complexity of coloring by supergraphs of bipartite graphs;Bang-Jensen,1990
5. The Complexity of Generalized Colorings;MacGillivray,1990