एपीए उद्धरण

Radha,S, & Sankhyan,Amar Singh. (2004). Environmental challenges of the 21st century. Deep & Deep.

शिकागो स्टाइल उद्धरण

Radha,S, और Sankhyan,Amar Singh. Environmental Challenges of the 21st Century. New Delhi: Deep & Deep, 2004.

एमएलए उद्धरण

Radha,S, और Sankhyan,Amar Singh. Environmental Challenges of the 21st Century. Deep & Deep, 2004.