Patents.
4,829,529; 4,853,940; 4,859,016; 4,896,324; 4,862,469; 4,888,776; 4,900,150; 4,870,653; 4,881,237; 4,871,253; 4,907,235; 4,905,247; 4,907,237; 4,922,495; 4,930,136; 4,942,582; 4,932,030; 4,949,347; 4,958,908; 4,968,887; 4,961,202; 4,961,618; 4,973,119; 4,973,125; 4,974,923; 4,973,120; 4,974,228;