- Wert, S., and B. Roettgering. 1967. Aerial survey of insect-caused mortality—operation recorder gathers data quickly, cheaply. United States Department of Agriculture, Forest Service, Pacific Southwest Forest and Range Experiment Station, Research Note PSW-150. 4 p.
- Wert, S., and B. Roettgering. 1968. Douglas-fir beetle survey with color photos; aerial color photography sampling techniques applied to an epidemic in California yielded important forest mortality data quickly and economically . Photogrammetric Engineering 34:1243-1248.