Ashton-Jones, N. J. (2000). A guide to understanding the environment. National Integrated Protected Areas Programme, Protected Areas and Wildlife Bureau.
Lua i Stíl Chicago (17ú heag.)Ashton-Jones, Nick J. A Guide to Understanding the Environment. Quezon City: National Integrated Protected Areas Programme, Protected Areas and Wildlife Bureau, 2000.
Lua MLA (9ú heag.)Ashton-Jones, Nick J. A Guide to Understanding the Environment. National Integrated Protected Areas Programme, Protected Areas and Wildlife Bureau, 2000.
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