Patents.
4,511,783; 4,523,799; 4,543,484; 4,546,230; 4,546,231; 4,595,261; 4,598,405; 4,606,608; 4,615,582; 4,616,929; 4,616,930; 4,617,670; 4,618,210; 4,618,214; 4,621,925; 4,623,219; 4,624,526; 4,624,526; 4,626,075; 4,628,515; 4,629,297; 4,629,879; 4,639,095; 4,639,096; 4,640,586; 4,639,139; 4,640,615; 4,641,928; 4,641,929; 4,641,934; 4,642,113; 4,643,536; 4,643,575; 4,643,576; 4,643,033; 4,643,515; 4,645,302; 4,643,534; 4,645,300; 4,645,312; 4,645,340; 4,647,158; 4,647,160; 4,647,161; 4,647,778.