Patents.
3,288,018; 3,419,329; 3,432,221; 3,432,766; 3,432,768; 3,436,665; 3,463,571; 3,482,138; 3,479,109; 3,482,899; 3,482,901; 3,484,599; 3,485,553; 3,489,941; 3,495,034; 3,495,913; 3,497,285; 3,497,286; 3,497,287; 3,497,288; 3,498,695; 3,500,055; 3,500,736; 3,501,216; 3,502,388; 3,502,414; 3,503,670; 3,504,295.