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Cornet, Bruce, 1977, Palynostratigraphy and age of the Newark Supergroup: Pennsylvania State University, unpublished Ph.D. dissertation, 505 p. abstract
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Wood, C. R., 1980, Groundwater resources of the Gettysburg and Hammer Creek Formations, southeastern Pennsylvania: Pennsylvania Geological Survey, 4th ser., Water Resource Report 49, 87 p. (web release).