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math.CO2002
Even circuits of prescribed clockwise parity
Ilse Fischer, C. H. C. Little
We show that a graph has an orientation under which every circuit of even length is clockwise odd if and only if the graph contains no subgraph which is, after the contraction of a…
math.CO2000
A characterisation of Pfaffian near bipartite graphs
Ilse Fischer, C. H. C. Little
In 1967 Kasteleyn introduced a powerful method for enumerating the 1-factors of planar graphs. In fact his method can be extended to graphs which permit an orientation under which…
math.CO1999
Towards a characterisation of Pfaffian graphs
Charles H. C. Little, Franz Rendl, Ilse Fischer
A bipartite graph G is known to be Pfaffian if and only if it does not contain an even subdivision H of such that contains a 1-factor. However a general characte…