1. 1Reichman Rheinhold , "Spark Plug," U. S. Pat. 1,799,225, April 7, 1931 .
2. 2Ryshkewitch Eugene , One Component Oxide Ceramics on Basis of Physical Chemistry (Oxydkeramik der Einstoffsysteme vom Standpunkt der Physikalischen Chemie) . Springer-Verlag, Berlin, 1948 , 280 pp.Ceram. Abstr., 1949, October, p. 233g.
3. 3(a)T. G. McDougal, A. H. Fessler, and Karl Schwartz-walder "Spark-Plug Insulator ," U. S. Pat. 2,120,338, June 14, 1938; Ceram. Abstr., 17 [9] 309(1938).
4. 3(b)T. G. McDougal, A. H. Fessler, and H. B. Barlett , "Ceramic Body for Spark-Plug Insulators," U. S. Pat. 2,177,943. October 31, 1939 .