1. Qualitative economics and the scope of the correspondence principle;Bassett;Econometrica,1968
2. Consistency in marked digraphs;Beineke;J. Math. Psych.,1978
3. Graphes et hypergraphes;Berge,1970
4. Structural balance : a generalization of Heider's theory;Cartwright;Psychol. Review,1956
5. Shortest paths methods: 1. Reaching, pruning and buckets;Denardo;Oper. Res.,1979