1. L.M. Cook, K.-H. Mader and R. Schnabel, US Patent No. 4 434 191 (1981) Schott Glass Technologies, Inc., Duryea, Pa., USA.
2. PROSPECT “Radiation shielding glasses and radiation shielding windows by Schott. It is our stringent quality requirements that enable you to work in safety” (1978) Schott Glaswerke, Mainz, FRG.
3. Prospect “The advantage of DESAG non-reflective glass, you see, is that you don't see it” (1981) Deutsche Spezialglas AG, Grünenplan, FRG.