Kopera, J. P. Preliminary bedrock geologic map of the Ayer quadrangle, Massachusetts. Open-File Report (2006). at <http://www.geo.umass.edu/stategeologist/>

Kopera, J. P., Alvord, D. C., Jahns, R. H., Willard, M. E. & White, W. S. Preliminary bedrock geologic map of the Westford quadrangle, Massachusetts. Open-File Report (2009).

Kopera, J. P., Mabee, S. B. & Powers, D. C. Preliminary fracture characterization map of the Ayer quadrangle, Massachusetts. Open-File Report (2006).