Patents.
4,746,798; 4,750,795; 4,755,015; 4,755,016; 4,763,994; 4,767,172; 4,770,502; 4,776,676; 4,778,259; 4,798,436; 4,798,438; 4,801,795; 4,803,353; 4,813,767 and 4,840,463; 4,813,769; 4,818,051; 4,822,145; 4,822,150; 4,835,391; 4,838,637; 4,838,646; 4,838,666; 4,838,667; 4,838,668; 4,840,463; 4,840,468; 4,840,469; 4,842,394; 4,844,613; 4,830,444.