00781nam a2200205Ia 4500 CTU_219270 210402s9999 xx 000 0 und d 333.72 F771 The foundations of national prosperity : Studies in the conservation of permanent national resources Richard T. Ely, ... [et al.] New York The Macmillan Comapny 1918 Conservation and economic theory; Conservation and economic evolution; Conservation of certain mineral resources; Conservation of human resources. Tài nguyên thiên nhiên,Natural resources Hoa Kỳ,United States Trúc Trung tâm Học liệu Trường Đại học Cần Thơ