Aerial observer's guide to recognizing and reporting southern pine beetle spots
Billings, Ronald F., Doggett, Coleman
Aerial observer's guide to recognizing and reporting southern pine beetle spots - Washington 1980 - 19 p. - No. 560; United States Departm .
Aerial observer's guide to recognizing and reporting southern pine beetle spots - Washington 1980 - 19 p. - No. 560; United States Departm .