Hepinstall, J.A., S.A. Sader, W.B. Krohn, R.B. Boone, and R.I. Bartlett. 1999. Development and Testing of a Vegetation and Land Cover Map of Maine. Maine Agricultural and Forest Experiment Station Technical Bulletin 173.

Krohn, W.B., R.B. Boone, and S.L. Painton. 1999. Quantitative delineation and characterization of hierarchical biophysical regions of Maine. Northeastern Naturalist 6:125-150.

Krohn, W.B., R.B. Boone, S.A. Sader, J.A. Hepinstall, S.M. Schaefer, and S.L. Painton. 1998. Maine Gap Analysis-a geographic analysis of biodiversity. Final contract report to USGS Biological Resources Division, Gap Analsis Program, Moscow, ID.