M. Chein and M. Mugnier, Graph-based Knowledge Representation: Computational Foundations of Conceptual Graphs, 2009.
URL : https://hal.archives-ouvertes.fr/lirmm-00355336

J. F. Sowa, Conceptual Graphs for a Data Base Interface, IBM Journal of Research and Development, vol.20, issue.4, pp.336-375, 1976.
DOI : 10.1147/rd.204.0336

J. F. Sowa, On conceptual structures, Artificial Intelligence, vol.34, issue.3, 1984.
DOI : 10.1016/0004-3702(88)90069-0