Hero (1899). "Pneumatika, Book ΙΙ, Chapter XI". Herons von Alexandria Druckwerke und Automatentheater (in Greek and German). Wilhelm Schmidt (translator). Leipzig: B.G. Teubner. pp. 228–232.
Ward English, Paul (June 21, 1968). "The Origin and Spread of Qanats in the Old World". Proceedings of the American Philosophical Society. 112 (3). JSTOR: 170–181. JSTOR986162.