1. 2.Theophilus, On Divers Arts, edited and translated by J.G. Hawthorneand C.S. Smith (Dover Publications, New York, 1963).
2. A study of french medieval glass composition
3. 4. Cox A. and Gillies K.J.S. , Glastechn. Ber.,61, 75-84 (1988).
4. 5. Turner W.E.S. quoted in Hawthorne and Smith, ref.2
5. 14. Sayre E.V. and Smith R.W. in Archaeological Chemistry edite'd by M.Levey (Philadelphia, 1967), 279-311.