Backus, John (1981). Function level programs as mathematical objects. New York, New York, USA: ACM Press. doi:10.1145/800223.806757.
Solov'ev, S.V. (1983). "The category of finite sets and Cartesian closed categories". J Math Sci. 22 (3): 1387–1400. doi:10.1007/BF01084396. S2CID122693163.
Solov'ev, S.V. (1983). "The category of finite sets and Cartesian closed categories". J Math Sci. 22 (3): 1387–1400. doi:10.1007/BF01084396. S2CID122693163.