For the first time, the concept of the combinator and the theory based on it were formulated by M.I. Sheinfinkel in the work of Schonfinkel (1924) even before the appearance of lambda-calculation. Shortly thereafter, similar results were obtained by Curry, regardless of Sheinfinkle and Church. When Carey got acquainted with Sheinfunkel's work, he attempted to contact him, but by this time Sheinfunkel was in a psychiatric clinic.

Introduction to Functional Programming.