Smith, P. M., & Warr, K. E. (1991). Global environmental issues.
Chicago Edition CitationSmith, Paul M., i Kiki; Ed Warr. Global Environmental Issues. London, Hodder & Stoughton, 1991.
Cita MLASmith, Paul M., i Kiki; Ed Warr. Global Environmental Issues. 1991.
Atenció: Aquestes cites poden no estar 100% correctes.