Dyfyniad APA

Perman, R. (2011). Natural resource and environmental economics (4th ed.). Pearson Education.

Dyfyniad Arddull Chicago

Perman, Roger. Natural Resource and Environmental Economics. 4th ed. Harlow, Essex, Eng: Pearson Education, 2011.

Dyfyniad MLA

Perman, Roger. Natural Resource and Environmental Economics. 4th ed. Pearson Education, 2011.

Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.