- Christiansen, E., and R. Horntvedt. 1983. Combined Ips/Ceratocystis attack on Norway spruce, and defence mechanisms of the trees . Zeitschrift fur Angewandte Entomologie 96:110-118.
- Horntvedt, R. 1983. Artificial inoculation with Ips typographus-associated blue-stain fungi can kill healthy Norway spruce trees. Meddelelser fra det Norsk Institutt for Skogforskning 38(4). 20 p.
- Horntvedt, R., and E. Christiansen. 1979. Gammelskog og grantorke . Norsk Skogbruk 25:21-23.
- Horntvedt, R. 1988. Resistance of Picea abies to Ips typographus tree response to monthly inoculations with Ophiostoma polonicum, a beetle transmitted blue-stain fungus . Scandinavian Journal of Forest Research 3:107-114.
- Horntvedt, R., E. Christiansen, H. Solheim, and S. Wang. 1983. Artificial inoculation with Ips typographus-associated blue-stain fungi can kill healthy Norway spruce trees. Meddelelser fra Norsk Institutt for Skogforskning 38(4). 20 pp. (Listed in Wood & Bright 1987 under 1st author only).