Patents.
4,712,879; 4,713,824; 4,714,308; 4,721,349; 4,723,842; 4,728,183; 4,729,372; 4,732,148; 4,737,021; 4,743,092; 4,744,615; 4,744,620; 4,746,179; 4,747,655; 4,747,661; 4,747,675; 4,747,676; 4,747,677; 4,747,678; 4,749,258; 4,749,259; 4,749,263; 4,749,264; 4,749,265; 4,749,266; 4,749,267; 4,749,840; 4,749,851; 4,749,854; 4,750,820; 4,752,121; 4,753,502; 4,753,503; 4,753,504; 4,753,520; 4,753,522; 4,753,506; 4,753,523; 4,755,027; 4,755,030; 4,756,591; 4,756,608;