Lucas, P. and Walk, K "On the formal description of PL/I"

Halpern, Mark I and Shaw Christopher J (eds) (1969) Halpern, Mark I and Shaw Christopher J (eds) "Annual Review in Automatic Programming" (6) 1969 Pergamon Press, Oxford  

Languages mentioned PL/I {1964} Programming Language One Vienna Definition Language {1965} Formal language description language