Wills, I. R. (2007). Economics and the environment: A signalling and incentives approach (2nd ed.). Allen & Unwin.
Chicago-viite (17. p.)Wills, Ian R. Economics and the Environment: A Signalling and Incentives Approach. 2nd ed. St. Leonards, NSW: Allen & Unwin, 2007.
MLA-viite (8. p.)Wills, Ian R. Economics and the Environment: A Signalling and Incentives Approach. 2nd ed. Allen & Unwin, 2007.
Varoitus: Nämä viitteet eivät aina ole täysin luotettavia.