↑Geoffrey Sampson(1985).Writing Systems.Stanford University Press.pp.80-81.ISBN0804717567
↑Joseph Naveh(1987)[1982].Early History of the Alphabet(2nd ed.).Hebrew University.p.25.ISBN9652234362
↑Peter T. Daniels(1996).“The First Civilizations”.InPeter T. Daniels; William Bright.The World's Writing Systems.Oxford University Press.p.29.ISBN0195079930