Patents.
4,603,938; 4,610,499; 4,628,206; 4,643,514; 4,644,173; 4,653,857; 4,686,858; 4,688,228; 4,689,794; 4,696,012; 4,699,468; 4,701,924; 4,704,583; 4,703,491; 4,703,992; 4,711,512; 4,704,033; 4,705,300; 4,711,544; 4,711,576; 4,708,480; 4,712,852; 4,712,851; 4,712,882; 4,712,883; 4,712,884; 4,713,820; 4,713,823; 4,714,307; 4,714,310; 4,714,309; 4,715,693; 4,715,670; 4,715,699; 4,717,228; 4,717,224; 4,717,225; 4,717,230; 4,717,239; 4,717,245; 4,717,821; 4,717,822; 4,718,069; 4,718,749; 4,718,752; 4,718,764; 4,719,635; 4,720,158; 4,720,177; 4,720,179; 4,720,180; 4,720,181; 4,720,183; 4,720,632; 4,721,371; 4,721,385; 4,722,605; 4,723,827.