Silvio Meira and Cássio Santos. 1991.
 SmallVDM: An Environment for Formal Specification and Prototyping in Smalltalk. In <em>Proceedings of the 5th Brazilian Symposium on Software Engineering</em>, October 23, 1991, Ouro Preto/MG, Brasil. SBC, Porto Alegre, Brasil, 221-236. DOI: <a href="https://doi.org/10.5753/sbes.1991.24269">https://doi.org/10.5753/sbes.1991.24269</a>.