Sellars, R. W. (1997). Preserving nature in the national parks: A history : with a new preface and epilogue. Yale University Press.
Dyfyniad Arddull ChicagoSellars, Richard West. Preserving Nature in the National Parks: A History : With a New Preface and Epilogue. New Haven: Yale University Press, 1997.
Dyfyniad MLASellars, Richard West. Preserving Nature in the National Parks: A History : With a New Preface and Epilogue. Yale University Press, 1997.
Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.