Patents.
4,666,250; 4,674,091; 4,690,489; 4,674,100; 4,678,268; 4,687,295; 4,687,926; 4,688,879; 4,688,880; 4,688,903; 4,688,904; 4,690,485; 4,690,513; 4,690,517; 4,690,518; 4,691,996; 4,691,999; 4,693,545; 4,693,565; 4,693,566; 4,693,568; 4,695,119; 4,695,120; 4,695,132; 4,695,134; 4,695,136; 4,696,572; 4,697,869; 4,697,892.