N. J. Collar: The Philippine Eagle: one hundred years of solitude. Oriental Bird Club Bulletin 24, 1996 Online
web.archive.org
Dieldre S. Harder, Rex Labao, Florence Ivy Santos: Saving the Philippine Eagle: How Much would It Cost and are Filipinos Willing to Pay for It?, August 2006 (Online (Memento vom 11. Januar 2016 im Internet Archive); PDF; 570 kB)