Gottfried, B. S. (1973). PL/I programmer's reference guide. Quantum.
Lua i Stíl Chicago (17ú heag.)Gottfried, Byron S. PL/I Programmer's Reference Guide. New York: Quantum, 1973.
Lua MLA (8ú heag.)Gottfried, Byron S. PL/I Programmer's Reference Guide. Quantum, 1973.
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