Journal of Statistical Physics, Vol. 58, Nos. 3/4, 1990. p. 553-574.
Consider a twc-rooted graph G, the edges of which are directed in such a way that there are no cycles and every edge belongs to some self-avoiding walk from root u to root v which follows the direction of the edges. A u-v backbone of G is a subgraph formed by taking the union of any subset of directed self-avoiding walks from u to v...