- Bedard, W. D. (. 1964. Variation in capacity of Ips confusus to reach attractive hosts. Pergammon Press, Oxford 203 pp..
- Gerhold, H. D., and Et. All. 1966. Breeding pest-resistant trees. Pergamon Press, Oxford 505+ix pp..
- Gerhold, H. D., and e. al. 1966. Breeding pest-resistant trees. Pergamon Press, Oxford, Proceedings of a N.A.T.O. and N.S.F. advanced study institute on genetic improvement for disease and insect resistance of forest trees. University Park, Pennsylvania 505 + ix.