- Gehrken, U. 1984. Winter survival of an adult bark beetle Ips acuminatus Gyll . Journal of Insect Physiology 30:421-429.
- Gehrken, U., and K. E. Zachariassen. 1977. Variations in the cold-hardiness of hibernating Ips acuminatus Gyllenhal (Col, Scolytidae) related to the sun exposure of the habitat . Norsk Entomologisk Tidsskrift 24:149-152.
- Gehrken, U. 1985. Physiology of diapause in the adult bark beetle, Ips acuminatus Gyll., studied in relation to cold hardiness. Journal of Insect Physiology 31: 909-916.
- Gehrken, U. 1989. Supercooling and thermal hysteresis in the adult bark beetle Ips acuminatus Gyll . Journal of Insect Physiology 35:347-352.
- Gehrken, U. 1992. Inoculative freezing and thermal hysteresis in the adult beetles Ips acuminatus and Rhagium inquisitor . Journal of Insect Physiology 38:519-524.
- Gehrken, U. 1995. Correlative influence of gut appearance, water content and thermal hysteresis on whole body supercooling of adult bark beetles, Ips acuminatus Gyll . Comparative Biochemistry and Physiology A 112:207-214.