Jones, C. (1989). Probabilistic Non-determinism, 198.
Jones, C., & Plotkin, G. (1989). A Probabilistic Powerdomain of Evaluations. In Proceedings of the Fourth Annual Symposium on Logic in Computer Science (pp. 186–195). Piscataway, NJ, USA: IEEE Press. Retrieved from http://dl.acm.org/citation.cfm?id=77350.77370
Plotkin, G. D. (1977). LCF considered as a programming language. Theoretical Computer Science, 5(3), 223–255. https://doi.org/10/dc7fdn