Sass, Benjamin. Studia Alphabetica: On the Origin and Early History of the Northwest Semitic, South Semitic and Greek Alphabets. Orbis Biblicus et Orientalis, 102. Freiburg: Universitätsverlag, 1991.
Sass discusses the emergence of the Northwest Semitic alphabet and its relationships to the South Semitic and Greek alphabets. He argues for an 18th Century date for the development of the Northwest Semitic alphabet based on parallels to “almost alphabetic” writing of foreign names in Middle Kingdom Egyptian. The South Semitic alphabets contain many letters resembling Phoenician forms of the 10th-11th centuries which is most likely the period of the beginning of the South Arabian alphabet.
On the issue of vowel letters, he claims that the use of matres lectionis for /a/, /i/, and /u/ existed from the beginning in the Egyptian “alphabetic” writing of the Middle Kingdom. The reed sign, used for alep, also marked medial and final /a/ and /i/. Egyptian w also served as a mater for /u/. However, it is uncertain why the inhabitants of southern Canaan “were content to adopt only the consonants and did not from the very start take over the matres lectionis.”Orthography, Sass, Benjamin