In search of York : the slave who went to the Pacific with Lewis and Clark / by Robert B. Betts. - Boulder : Colorado Associated Univ. press, [c.1985]. - x, 182 p. : ill. + [4] inset l., ill. ; 26 cm.см.. - ბიბლიოგრ.: გვ. 173-178. - ISBN 0-87081-144-4[MFN: 40083]