Geohydrology and simulation of steady-state flow conditions in regional aquifer systems in Cretaceous and older rocks underlying Kansas, Nebraska, and parts of Arkansas, Colorado, Missouri, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming / D. C. Signor, J. O. Helgesen, D. G. Jorgensen, R. B. Leonard, 1997. - VIII,105 p. p. - Текст : непосредственный.
Helgesen J.O. Hydrology of the Great Plains aquifer system in Nebraska,Colorado,Kansas,and adjacent areas / J. O. Helgesen, R. B. Leonard, R. J. Wolf, 1993. - VII,E80 p. p. - Текст : непосредственный.
Analysis of regional aquifers in the Central Midwest of the United States in Kansas, Nebraska, and parts of Arkansas, Colorado, Missouri, New Mexico, Oklahoma, South Dakota, Texas and Wyoming-Summary / D.G.Jorgensen,J.O.Helgesen,D.C.Signor и др., 1996. - VII,67 p. p. - Текст : непосредственный.