1. General Electric Co. Engineering Division Lamp Dept. Bulletin LD-1
2. General Electric Co. Engineering Division Lamp Dept. Bulletin LD-103
3. Maksutov D.D. USSR. Patent No. 40859 (1932).
4. Land E. H. U. S. Patent No. 2 287 556 (1942).
5. Shurcliff W. A. U. S. Patent No. 2 369 317 (1945).