APA
Engel J. R., Engel J. G., International Union for Conservation of Nature and Natural Resources & Conference on Conservation and Development: Implementing the World Conservation Strategy. (1990). Ethics of environment and development. Tucson: University of Arizona Press.
Chicago
Engel J Ronald, Engel Joan Gibb, International Union for Conservation of Nature and Natural Resources and Conference on Conservation and Development: Implementing the World Conservation Strategy. 1990. Ethics of environment and development. Tucson: University of Arizona Press.
Harvard
Engel J. R., Engel J. G., International Union for Conservation of Nature and Natural Resources and Conference on Conservation and Development: Implementing the World Conservation Strategy. (1990). Ethics of environment and development. Tucson: University of Arizona Press.
MLA
Engel J Ronald, Engel Joan Gibb, International Union for Conservation of Nature and Natural Resources and Conference on Conservation and Development: Implementing the World Conservation Strategy. Ethics of environment and development. Tucson: University of Arizona Press. 1990.