Patents.
4,610,513; 4,610,516; 4,615,588; 4,615,589; 4,616,132; 4,616,908; 4,620,768; 4,620,774; 4,620,775; 4,620,790; 4,620,792; 4,621,888; 4,621,904; 4,621,891; 4,621,905; 4,621,909; 4,621,911; 4,623,214; 4,623,224; 4,624,535; 4,623,225; 4,624,528; 4,624,536; 4,624,538; 4,626,076; 4,626,082; 4,626,679; 4,627,685; 4,627,690; 4,627,729; 4,627,730; 4,629,291; 4,629,292; 4,629,293; 4,629,294.