1. Bellman, R. E. [1958]. ?On a routing problem,? Quart. Appl. Math., 16, 87?90.
2. Bonsall, P. W. [ 1974 ]. ?Implementation of various cost functions in tree-building algorithms,? Institute for Transport Studies, Working Paper 47 (unpublished).
3. Bonsall P. W., Cripps, E. L., Goodman, P. R., Hankin, A., Mackett, R. L., Sanderson, L., Senior, M. L., Southworth, F., Spence, R., Williams, H. C. W. L. and Wilson, A. G. [1974]. ?A transport model for West Yorkshire,? Institute for Transport Studies, Working Paper 46 (unpublished).
4. Coventry Transportation Study [1972]. Report on Phase Two, Technical Report, Ch 28?68, City of Coventry, December.
5. Dijkstra, E. W. [1959]. ?A note on two problems in connection with graphs,? Numer. Math. 1, 269?271.