Patents.
4,762,416; 4,776,700; 4,765,740; 4,777,825; 4,786,173; 4,794,598; 4,795,258; 4,795,259; 4,803,687; 4,803,713; 4,807,998; 4,818,087; 4,818,109; 4,824,252; 4,807,999; 4,834,538; 4,837,774; 4,829,528; 4,841,541; 4,852,968; 4,880,296; 4,859,017; 4,856,864; 4,867,518; 4,872,738.