Operations preserving the pfaffian property of a graph
Charles H. C. Little, Franz Rendl · Journal of the Australian Mathematical Society Series A Pure Mathematics and Statistics · 1991
Abstract Pfaffian graphs are those which can be oriented so that the 1-factors have equal sign, as calculated according to the prescription of Kasteleyn. We consider various operations on graphs and examine their effect on the Pfaffian property. We show that the study of Pfaffian graphs may be reduced to the case of subcubic graphs (graphs in which no vertex has degree greater than 3) or bricks (3-connected bicritical graphs).