Vergara, R. (1973). Programmed instruction on the English past tense for grade five. publisher not identified].
Čikaški stil citiranja (17. izdanje)Vergara, Ruperta. Programmed Instruction on the English Past Tense for Grade Five. [Quezon City: publisher not identified], 1973.
MLA način citiranja (9. izdanje)Vergara, Ruperta. Programmed Instruction on the English Past Tense for Grade Five. publisher not identified], 1973.
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