1. A. Berman and R.J. Plemmons,Non-negative matrices in the mathematical sciences (Academic Press, New York, 1979).
2. V. Cerny, “A thermodynamical approach to the travelling salesman problem: An efficient simulation algorithm”,Journal of Optimization Theory and Applications (1984), to appear.
3. A.W.F. Edwards, “Minimal evolution” (Unpublished, 1966).
4. B. Everitt,Cluster analysis (Heineman Educational Books, London, 1977).
5. M.R. Garey and D.S. Johnson,Computers and intractability: A guide to the theory of NP-completeness (W.H. Freeman, San Francisco, 1979).