Patents.
4,714,339; 4,733,561; 4,737,642; 4,746,201; 4,750,162; 4,752,934; 4,761,050; 4,761,059; 4,767,190; 4,763,974; 4,767,195; 4,767,934; 4,768,862; 4,773,739; 4,773,754; 4,776,678; 4,778,236; 4,779,959; 4,781,426; 4,785,169; 4,791,646; 4,792,201; 4,792,212; 4,792,213; 4,793,676; 4,796,962; 4,796,965; 4,796,984; 4,798,450; 4,798,462; 4,798,463; 4,803,737.