See Frank Moore Cross and Thomas Lambdin, “A Ugaritic Abecedary and the Origins of the Proto-Canaanite Alphabet,” Bulletin of the American Schools of Oriental Research 160 (1960), pp. 21–26, now conveniently available in Frank Moore Cross, Leaves from an Epigrapher’s Notebook (Winona Lake, IN: Eisenbrauns, 2003), pp. 313–316.