James L. Murphy, "Two Older 'New" Old Maps of the Newark Earthworks," Ohio Archaeologist 45 no. 2 (Spring 1995): 4-7.
An unpublished map of the Newark Earthworks, Licking Co., Ohio, is attributed to Rev. John Pogue Campbell and dates to ca. 1808-1814. An earlier map by an unknown hand is also illustrated and described.