Patents.
3,463,575; 3,468,598; 3,473,866; 3,474,253; 1505; 3,476,026; 3,476,457; 3,476,459; 3,476,461; 3,476,462; 3,477,776; 3,478,661; 3,479,510; 3,481,664; 3,481,666; 3,482,102; 3,482,900; 3,482,902; 3,484,152; 3,485,549; 3,485,550; 3,485,551; 3,485,554; 3,485,557.