Patents.
4,852,983; 4,861,124; 4,906,095; 4,907,849; 4,871,220; 4,909,628; 4,869,593; 4,898,470; 4,893,910; 4,915,476; 4,919,527; 4,921,335; 4,925,271; 4,929,063; 4,932,762; 4,938,572; 4,940,309; 4,929,077; 4,932,737; 4,946,233; 4,936,653; 4,939,368; 4,943,146; 4,940,305; 4,945,248; 4,941,719; 4,942,299; 4,946,279; 4,947,034; 4,943,144; 4,940,333; 4,929,050; 4,946,231; 4,947,044; 4,947,400.