Congress of the International Association of Hydrogeologists (IAH 1998 Gambling with groundwater : physical, chemical, and biological aspects of aquifer-stream relations ; proceedings of the joint meeting of the XXVIII congress of the International Association of Hydrogeologists and the annual meeting of the American Institute of Hydrologists, Las Vegas, Nevada, USA, 28 September - 2 October 1998 1971 Congress of Tokyo (Asian Regional Conference) 1971 - International Association of Hydrogeologists 1967 Congress of Istanbul 1967 - International Association of Hydrogeologists