Enumeration of directed trees
K. Sankara Rao, V.V. Bapeswara Rao, Vempati G. K. Murti · Proceedings of the IEEE · 1971
A systematic method for the enumeration of all the directed trees of a graph is presented. A large memory is not required for implementation of the method on a computer. The algorithm employs a new matrix termed "branch-chord incidence matrix" and a number system in which the radix is varied for each digit.