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

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

Kopera, J. P. & Hansen, W. R. Preliminary Bedrock Geologic Map of the Hudson 7.5' Quadrangle Worcester and Middlesex Counties, Massachusetts. Open File Report (2014).

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