@book{145531,
	author = {Helgesen, John O. and Leonard, Robert B.},
	title = {Hydrology of the Great Plains aquifer system in Nebraska, Colorado, Kansas, and adjacent areas},
	publisher = {U.S. G.P.O.},
	year = {1993.},
	series = {Regional aquifer-system analysis--Central Midwest},
	address = {Washington}
}