Transformations of a Graph Increasing its Laplacian Polynomial and Number of Spanning Trees.

Alexander K. Kelmans Transformations of a Graph Increasing its Laplacian Polynomial and Number of Spanning Trees. 35-48 1997 18 Eur. J. Comb. 1 http://dx.doi.org/10.1006/eujc.1995.0077 db/journals/ejc/ejc18.html#Kelmans97