See for example: a. Petrie, Flinders. Social Life in Ancient Egypt (1970 reprint, 1923 original), page 176. New York: Cooper Square. b. Rappoport, S. (Doctor of Philosophy, Basel). History of Egypt (undated, early 20th century), Volume 12, Part B, Chapter V: "The Waterways of Egypt, " pages 248—251. London: The Grolier Society. c. Silver, Morris. Ancient Economies II (Apr. 6, 1998), «5c. Evidence for Earlier Canals.» ANCIENT ECONOMIES II, retrieved Aug. 8, 2008. Economics Department, City College of New York.
