History 177 General 173 Eau 134 Histoire 106 SOCIAL SCIENCE 95 HISTORY 89 Water 82 POLITICAL SCIENCE 53 Purification 53 Services d'eau 52 Épuration 51 BUSINESS & ECONOMICS 47 Water-pipes 47 State & Local 40 Water-supply 39 Gestion 37 Management 36 Tuyaux d'eau 36 Waterworks 36 Approvisionnement 35 Water utilities 35 BIOGRAPHY & AUTOBIOGRAPHY 32 Politics and government 31 Distribution 28 Reference 28 LITERARY CRITICISM 27 Social aspects 26 West (AK, CA, CO, HI, ID, MT, NV, UT, WY) 26 Design and construction 25 Drinking water 24