Minsky, Marvin (1967). Computation: Finite and Infinite Machines (1st ed.). Englewood Cliffs, New Jersey, USA: Prentice-Hall, Inc. p. 214. In particular see chapter 11: Models Similar to Digital Computers and chapter 14: Very Simple Bases for Computability. In the former chapter he defines "Program machines" and in the later chapter he discusses "Universal Program machines with Two Registers" and "...with one register", etc.
Minsky, Marvin (1961). "Recursive Unsolvability of Post's Problem of 'Tag' and Other Topics in Theory of Turing Machines". Annals of Mathematics. 74 (3): 437–455 [438, 449]. doi:10.2307/1970290. JSTOR1970290.
Minsky, Marvin (1961). "Recursive Unsolvability of Post's Problem of 'Tag' and Other Topics in Theory of Turing Machines". Annals of Mathematics. 74 (3): 437–455 [438, 449]. doi:10.2307/1970290. JSTOR1970290.