Patents.
4,639,138; 4,639,600; 4,640,618; 4,640,585; 4,641,026; 4,641,315; 4,641,311; 4,641,933; 4,641,971; 4,642,809; 4,643,519; 4,643,538; 4,639,138; 4,639,600; 4,640,618; 4,640,585; 4,641,026; 4,641,315; 4,641,311; 4,641,933; 4,641,971; 4,642,809; 4,643,519; 4,643,538; 4,639,138; 4,639,600; 4,640,618; 4,640,585; 4,641,026; 4,641,315; 4,641,311; 4,641,933; 4,641,971; 4,642,809; 4,643,519; 4,643,538; 4,639,138; 4,639,600; 4,640,618; 4,640,585; 4,641,026; 4,641,315; 4,641,311; 4,641,933; 4,641,971; 4,642,809; 4,643,519; 4,643,538; 4,643,574; 4,644,548; 4,647,204; 4,648,716; 4,652,132; 4,653,880; 4,653,917; 4,655,542; 4,655,547; 4,655,565; 4,657,344; 4,657,391; 4,658,389; 4,658,403; 4,660,929; 4,660,204; 4,660,205; 4,660,589; 4,661,964; 4,662,716; 4,662,722; 4,662,725; 4,666,256; 4,663,961; 4,664,486; 4,666,246; 4,666,257; 4,666,258; 4,666,259; 4,666,260; 4,668,054; 4,668,085; 4,668,860; 4,669,810;