On bounded treewidth duality of graphs
Jaroslav Nešetřil, Xuding Zhu · Journal of Graph Theory · 1996
We prove that for any integers m; k, there is an integer n0 such that if G is a graph of girth n0 then any partial k-tree homomorphic to G is also homomorphic to C2m+1 . As a corollary, every non-bipartite graph does not have bounded treewidth duality.