1. Ore, O.: Theory of graphs. American Mathematical Society Colloquium Publications, Providence (1962)
2. Kaufmann, A.: Introduction a la theorie des sous-ensemles flous. Masson, Paris (1977)
3. Christofides, N.: Graph Theory: An Algorithmic Approach. Academic press, London (1976)
4. Rosenfeld, A.: Fuzzy graphs. In: Zadeh, L.A., Fu, K.S., Shimura, M. (eds.) Fuzzy Sets and Their Applications, pp. 77–95. Academic Press, New York (1975)
5. Monderson, J., Nair, P.: Fuzzy Graphs and Fuzzy Hypergraphs. Heidelberg; New-York, Physica-Verl (2000)