1. S. L. Hakimi, On trees of a graph and their generation,J. Franklin Inst.,272 (1961), 347–359.
2. S. D. Bedrosian, Formulas for the number of trees in a network,I.R.E. Trans. on Circuit Theory, Vol. PGCT-8, No. 3 (1961), 363–364.
3. J. W. Moon, Enumerating labelled trees, inGraph Theory and Theoretical Physics, ed. by F. Harary (London, Academic Press, 1970).
4. L. Weinberg, Number of trees in a graph,Proc. I.R.E. 46 (1958), 1954–1955.
5. P. V. O'Neil andP. Slepian, An application of Feussner's method to tree counting,IEEE Trans. on Circuit Theory, Vol. CT-13, No. 3 (1966), 337–339.