Water balance in North America : proceedings of the symposium on "Water balance in North America," held at Banff, Alberta, Canada June 23-26, 1969 / edited by Arleigh H. Laycock, Martha Francisco, Thelma Fisher. - Laycock, Arleigh H.; Francisco, Martha; Fisher, Thelma, 1904- (Proceedings series (American Water Resources Association), 1969)