G.L. Steele et al, "The Evolution of Lisp"

[HOPL II] (1993) [ACM SIGPLAN] SIGPLAN Notices 28(03) March 1993 The second ACM SIGPLAN conference on History of programming languages (HOPL II)  

Languages mentioned EL1 {1970} Extensible Language SEUS {1993} SYSLISP {1979}