Holt, Richard C. "Teaching the fatal disease: (or) introductory computer programming using PL/I" pp8-23

[SIGPLAN] (1973) ACM SIGPLAN Notices 8(5) May 1973  

Languages mentioned PL/C {1970} Programming Language/Cornell PL/I {1964} Programming Language One PLUTO {1972} U Toronto Teching PL/I SP/k {1975}