Patents.
4,723,263; 4,728,192; 4,740,083; 4,747,111; 4,748,328; 4,748,646; 4,752,946; 4,753,529; 4,755,021; 4,755,051; 4,756,620; 4,759,627; 4,759,629; 4,762,415; 4,765,189; 4,765,739; 4,768,880; 4,773,758; 4,773,759; 4,777,660; 4,778,237; 4,778,239; 4,778,261; 4,779,943; 4,781,425; 4,782,228; 4,783,170; 4,787,721; 4,787,723; 4,784,449; 4,787,724; 4,788,866; 4,789,230; 4,790,636; 4,790,637; 4,790,638; 4,792,214; 4,792,215; 4,792,216; 4,792,217; 4,792,218; 4,792,219; 4,793,669.