- Cowan, B. D. 1965. The biologies of predators (Coleoptera: Cleridae) of the Douglas-fir beetle, Dendroctonus pseudotsugae Hopkins (Coleoptera: Scolytidae), in western Oregon. Unpublished thesis, Oregon State University, Corvallis.
- Cowan, B. D., and W. P. Nagel. 1965. Predators of the Douglas-fir beetle (Dendroctonus pseudotsugae) . Oregon Agricultural Experiment Station, Technical Bulletin 86:1-32.