Eagar, Christopher C.. Investigations of Balsam Woolly Aphid-Fraser Fir Interaction:  Feeding Site Characteristics and Wound Response. Knoxville, TN: The University of Tennessee, 1985.

Hay, Ronald L., and Christopher C. Eagar. Final Contract Report for Regional Chief Scientist, Southeast Regional Office, National Park Service On Stem Morphology and Physiology of Fraser Fir in Relation to Balsam Wolly Aphid. Knoxville, TN: University of Tennessee, 1981.

Hay, Ronald L., Christopher C. Eagar, and Kristine D. Johnson. Fraser Fir in the Great Smoky Mountains National Park: Its Demise by the Balsam Woolly Aphid (Adelges Piceae Ratz.). Knoxville, TN: Department of Forestry, University of Tennessee, 1978.

Hay, Ronald L., Christopher C. Eagar, and Kristine D. Johnson. Status of the Balsam Woolly Aphid in the Great Smoky Mountains National Park --- 1976 In Management Report. Gatlinburg, TN: Uplands Field Research Laboratory, 1976.