Patents.
3,226,228; 3,418,044; 3,420,150; 3,420,596; 3,421,096; 3,421,097; 3,426,294; 3,428,393; 3,438,689; 3,438,695; 3,442,191; 3,438,697; 3,443,858; 3,449,040; 3,449,041; 3,449,050; 3,449,565; 3,450,463; 3,450,477; 3,451,743; 3,453,035; 3,453,425; 3,454,321; 3,454,322; 3,454,326; 3,454,327; 3,454,338; 3,454,339; 3,454,715; 3,454,716; 3,455,623; 3,456,999; 3,457,002; 3,457,364; 3,457,401; 3,459,468; 3,459,469; 3,460,881; 3,460,886; 3,460,892;