Fosdick, Howard "High-level languages for operating systems development: a historical overview" pp31-37

[SIGPLAN] (1979) SIGPLAN Notices 14(07) July 1979  

Languages mentioned Basic Systems Language {1971} Forerunner of PL/S BCPL {1967} Basic CPL PL/I {1964} Programming Language One PL/S {1968} Programming Language/Systems PL360 {1965} Wirth's Algol 60-derived HLA for the 360 PL516 {1970}