The Black Barren spring Mineral Waters Natural Springs [Philadelphia? : s.n., 1872?] Black Barren Spring Co. Advertisements Text 16 p. nlm:nlmuid-101231153-bk 101231153 http://resource.nlm.nih.gov/101231153 English Pennsylvania The National Library of Medicine believes this item to be in the public domain : https://creativecommons.org/publicdomain/mark/1.0/