"Römer (crater)". Gazetteer of Planetary Nomenclature. USGS Astrogeology Research Program.
pubs.er.usgs.gov
The geologic history of the Moon, 1987, Wilhelms, Don E.; with sections by McCauley, John F.; Trask, Newell J. USGS Professional Paper: 1348. Plate 11: Copernican System (online)
