Gurcharan Singh. (2000). Pollution to purity of environment.
Chicago Style aipamenaGurcharan Singh. Pollution to Purity of Environment. New Delh, Deep & Deep Publications, 2000.
MLA aipamenaGurcharan Singh. Pollution to Purity of Environment. 2000.
Kontuz: berrikusi erreferentzia hauek erabili aurretik.