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Napoitelni Sistemi v N R Bǔlgarija
Grigorov, Slave, (1963)
Interbasin transfers of water. Economic issues and impacts
Howe, Charles Warren, (1971)
Proceedings of the Third Regional Technical Conference on Water Resources Development in Asia and the Far East, [Manila, Philippines, 4. - 10.12.1957]
(1958)