Patents.
4,706,253; 4,706,255; 4,711,514; 4,729,652; 4,737,000; 4,741,613; 4,744,641; 4,744,658; 4,749,247; 4,749,274; 4,751,387; 4,752,122; 4,753,512; 4,755,013; 4,755,014; 4,755,022; 4,755,038; 4,756,589; 4,756,601; 4,756,604; 4,758,058; 4,758,059; 4,758,061; 4,758,072; 4,758,073; 4,758,074; 4,758,086; 4,758,088; 4,758,089; 4,759,593; 4,759,594; 4,759,596; 4,759,610; 4,759,619; 4,759,624; 4,760,267; 4,761,048; 4,761,063; 4,761,064; 4,761,561; 4,766,308.