Sellars, R. W. (1997). Preserving nature in the national parks: A history : with a new preface and epilogue. Yale University Press.
Lua i Stíl Chicago (17ú heag.)Sellars, Richard West. Preserving Nature in the National Parks: A History : With a New Preface and Epilogue. New Haven: Yale University Press, 1997.
Lua MLA (9ú heag.)Sellars, Richard West. Preserving Nature in the National Parks: A History : With a New Preface and Epilogue. Yale University Press, 1997.
Rabhadh: Seans nach mbeach na luanna seo go hiomlán cruinn i ngach uile chás.