@incollection{GodsilGroetschelWelsh1995, author = {Chris Godsil and Martin Gr{\"o}tschel and Dominic Welsh}, title = {Combinatorics in Statistical Physics}, booktitle = {Handbook of combinatorics, Volume II, Part IV}, editor = {Ronald Graham and Martin Gr{\"o}tschel and L{\´a}szlo Lov{\´a}sz}, pages = {1925 -- 1954}, year = {1995}, }