Gregg, R. E. 1964. Distribution of the ant genus Formica in the mountains of Colorado. Leaflet. University of Colorado Museum 13:59-69.
Gregg, R. E. 1969a. Geographic distribution of the ant genus Formica (Hymenoptera: Formicidae). Proceedings of the Entomological Society of Washington 71:38-49. PDF
Gregg, R. E. 1972b. The northward distribution of ants in North America. Canadian Entomologist 104:1073-1091. PDF
Gregg, R. E. 1974. William Steel Creighton - An appreciation. Journal of the New York Entomological Society 82:67-75.
Grimaldi, D.; Agosti, D. 2000b. A formicine in New Jersey Cretaceous amber (Hymenoptera: Formicidae) and early evolution of the ants. Proceedings of the National Academy of Sciences of the United States of America 97:13678-13683. PDF
Grimaldi, D.; Engel, M. S. 2005. Evolution of the insects. Cambridge: Cambridge University Press, xv + 755 pp. PDF
Grolier Incorporated 1980. Academic American Encyclopedia. Volume 2. Princeton: Aretê Publishing Co., 384 pp.