Kopera, J. P. Bedrock geologic map of the Ayer 7.5? quadrangle, Worcester and Middlesex Counties, Massachusetts (2015). Open File Report

Peck, J. A. Digital conversion of Peck, J.H., 1975, Preliminary bedrock geologic map of the Clinton quadrangle, Worcester County, Mass., U.S. Geological Survey Open File Report 75-658. Digital Conversion (2012).

Kopera, J. P. Preliminary Bedrock Geologic Map of the area surrounding Shepley's Hill, Towns of Ayer and Devens, Massachusetts. Open-File Report (2008).

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