Patents.
4,705,361; 4,709,978; 4,717,238; 4,721,362; 4,725,141; 4,729,654; 4,743,112; 4,749,277; 4,756,584; 4,756,585; 4,759,616; 4,765,705; 4,768,847; 4,768,850; 4,768,851; 4,768,853; 4,768,854; 4,770,047; 4,770,505; 4,773,063; 4,773,753; 4,774,405; 4,774,406; 4,776,652; 4,778,262; 4,783,145; 4,778,244; 4,778,263; 4,783,156; 4,783,593.