Gaya APA

Kopp, R, J., Smith, V, K. (1993). Valuing Natural Assets, The Economics of Natural Resource Damage Assesment . Washington,DC: Resouces for the future.

Gaya MLA

Kopp, Raymond, J.., Smith, V., Kerry. "Valuing Natural Assets, The Economics of Natural Resource Damage Assesment". Washington,DC: Resouces for the future, 1993. Text.