Compositional characterisics of middle to upper tertiary volcanic rocks of the Bolivian Altiplano / E.A.duBray,S.Ludington,W.E.Brooks и др., 1995. - 30 p. - Текст : непосредственный.
Mineral resources of the Elkhorn Wilderness Study Area, Broadwater and Jefferson Counties, Montana / W.R.Greenwood,S.Ludington,W.R.Miller,W.F.Hanna, 1990. - 37 p. - Текст : непосредственный.