Ferguson, Jeffery R., and Craig E. Skinner (2003) Colorado Obsidian? Preliminary Results of a Statewide Database of Trace Elements Analysis. Southwestern Lore 69(4):35-50.
Larson, Mary Lou, Marcel Kornfield, and J.P. Matheson (1992) Archaeological Research at the Hutton-Pinkham Site, Eastern Colorado. Southwestern Lore 58(2):1-15.