Patents.
4,854,704; 4,870,648; 4,885,471; 4,887,900; 4,909,612; 4,925,307; 4,937,833; 4,938,563; 4,948,228; 4,958,914; 4,973,122; 4,972,699; 4,964,708;4,973,113;4,973,114; 4,973,115; 4,973,832; 4,977,560; 4,978,184; 4,979,827; 4,979,788; 4,979,807; 4,979,820; 4,979,824; 4,978,185; 4,983,825.