1. S.F Altschul and B. W. Erickson, Optimal Sequence Alignment Using Affine Gap Costs, Bull. Math. Biol. 48: 603–616, 1986.
2. R. Bellman and R. Kalaba, On Kth Best Policies, J. SIAM, 8(4):582–588, 1960.
3. S. Clarke, A. Krikorian and J. Rausen, Computing the N best Loopless Paths in a Network, J. Siam, 11 (4): 1096–1102, 1963.
4. R.F. Doolittle, Of Urfs and Orfs: A Primer on How to Analyze Derived Amino Acid Sequences, University Science Books, 1986.
5. R.F. Doolittle, edt. Methods in Enzymology, Volume 183: Molecular Evolution: Computer Analysis of Protein and Nucleic Acid Sequences, 1990.