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- Hagen, B. W., and M. D. Atkins. 1975. Between generation variability in the fat content and behavior of Ips paraconfusus Lanier. Zeitschrift fuer Angewandte Entomologie 79:169-172.
- Hagen, B. W., and M. D. Atkins. 1975. Between generation variability in the fat content and behavior of Ips paraconfusus Lanier . Zeitschrift fur Angewandte Entomologie 79:169-172.
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- Hagen, H. A. 1880. A new enemy of the black spruce, Abies nigra . Canadian Entomologist 12:121.
- Hagen, H. A. 1884. Scolytus rugulosus in branches of pear trees which were killed by pear blight . Canadian Entomologist 16:161-163.
- Hagen, K. S., and L. E. Caltagirone. 1968. A new nearctic species of Karpinskiella (Hymenoptera: Pteromalidae). Pan-Pacific Entomologist 44:241-248, 7 figs.