id: 04142067
dt: j
an: 04142067
au: Bang-Jensen, Jørgen; Hell, Pavol
ti: The effect of two cycles on the complexity of colourings by directed
    graphs.
so: Discrete Appl. Math. 26, No.1, 1-23 (1990).
py: 1990
pu: Elsevier Science B.V. (North-Holland), Amsterdam
la: EN
cc: 
ut: graph colouring; digraphs; directed cycles; H-colouring problem; NP-hard
ci: 
li: doi:10.1016/0166-218X(90)90017-7
ab: Let H be a fixed digraph. An H-colouring of a digraph D is a mapping f:
    V(D)$\to V(H)$ such that if xy is an arc in D then f(x)f(y) is an arc
    in H. The authors discuss various classes of digraphs H in which the
    existence of two directed cycles makes the H-colouring problem NP-hard.
rv: J.W.Moon