Langford, W. A., & Cocheba, D. J. [ca. 1978]. The wildlife valuation problem : a critical review of economic approaches. In Occasional paper / Canadian Wildlife Service [Book]. Ottawa: Minister of Supply and Services Canada.

LANGFORD, William A. und COCHEBA, Donald J., 1978. The wildlife valuation problem : a critical review of economic approaches. Ottawa: Minister of Supply and Services Canada. Occasional paper / Canadian Wildlife Service, 37. ISBN 0662015460.

Langford, W. A., und D. J. Cocheba. „The wildlife valuation problem : a critical review of economic approaches“. Occasional paper / Canadian Wildlife Service, book, Minister of Supply and Services Canada, 1978.

Langford, William A./Cocheba, Donald J.: The wildlife valuation problem : a critical review of economic approaches, . Occasional paper / Canadian Wildlife Service, Ottawa 1978.

Langford, W.A. und Cocheba, D.J. (1978), The wildlife valuation problem : a critical review of economic approaches, Occasional paper / Canadian Wildlife Service, Bd. , Minister of Supply and Services Canada, Ottawa.