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On universal graphs for planar oriented graphs of a given girth
1998
Discrete Mathematics
The oriented chromatic number o(H) of an oriented graph H is defined to be the minimum order of an oriented graph H' such that H has a homomorphism to H'. If each graph in a class ~ has a homomorphism to the same H', then H' is ~-universal. Let ~k denote the class of orientations of planar graphs with girth at least k. Clearly, ~3 ~ ~4 ~ ~5... We discuss the existence of ~k-universal graphs with special properties. It is known (see Raspaud and Sopena, 1994 ) that there exists a ~3-universal
doi:10.1016/s0012-365x(97)00276-8
fatcat:7rmeiloc3jcsvj5egmtj535iqa