Patents.
4,909,627; 4,991,919; 4,991,934; 4,991,946; 4,991,953; 4,995,693; 4,995,721; 4,997,242; 4,997,265; 4,998,801; 4,998,808; 5,000,529; 5,004,311; 4,746,216; 4,746,217; 4,986,651; 4,988,152; 4,988,154; 4,988,196; 4,989,929; 4,991,943; 4,991,945; 4,993,789; 4,993,792; 4,993,823.