P. W. Orr

Aerial photographic techniques for estimating damage by insects in western forests.

R. B. Pope, J. F. Wear, P. W. Orr, 1966 .

Forest insect and disease conditions in the United States, 1978.

P. W. Orr, H. D. Brown, 1980 .

Spruce Budworm in the Eastern United States

P. W. Orr, Daniel R. Kuceral, 2004 .