एपीए उद्धरण

UPSCPORTAL. (2012). Geography & Environment MCQs. UPSCPORTAL Publications.

शिकागो स्टाइल उद्धरण

UPSCPORTAL. Geography & Environment MCQs. Delhi: UPSCPORTAL Publications, 2012.

एमएलए उद्धरण

UPSCPORTAL. Geography & Environment MCQs. UPSCPORTAL Publications, 2012.