Eilertsen, Nils A. Investigation of Manganese Areas, Hammond Plantation and Hodgdon Townships, Southern District, Aroostook County, Maine, report, April 1958; (https://digital.library.unt.edu/ark:/67531/metadc38667/m1/1/: accessed November 19, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .