Spence, R. (1989). Clipper programming guide. Microtrend Books.
Lua i Stíl Chicago (17ú heag.)Spence, Rick. Clipper Programming Guide. San Marcos, CA: Microtrend Books, 1989.
Lua MLA (9ú heag.)Spence, Rick. Clipper Programming Guide. Microtrend Books, 1989.
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