1. Lee, R. J., and Binning, R. C., U.S. Patent 2,923,749 (Feb. 2, 1960).
2. Stuckey, J. M., U.S. Patent 2,930,754 (March 29, 1960).
3. Lee, R. J., U.S. Patent 2,947,687 (Aug. 2, 1960).
4. Binning, R. C., and Lee, R. J., U.S. Patent 2,953,502 (Sept. 20, 1960).
5. Stuckey, J. M., U.S. Patent 2,958,656 (Nov. 1, 1960).