Martín Abadi Luca Cardelli Benjamin C. Pierce Gordon D. Plotkin Dynamic Typing in a Statically Typed Language. 237-268 1991 13 ACM Trans. Program. Lang. Syst. 2 http://doi.acm.org/10.1145/103135.103138 db/journals/toplas/toplas13.html#AbadiCPP91