Patents.
4,205,900; 4,222,631; 4,239,341; 4,245,171; 4,249,139; 4,249,792; 4,253,021; 4,255,014; 4,255,765; 4,262,996; 4,263,810; 4,265,541; 4,266,138; 4,272,733; 4,274,703; 4,274,705; 4,274,733; 4,274,711; 4,275,302; 4,275,960; 4,276,517; 4,276,519; 4,277,127; 4,277,128; 4,277,137; 4,277,149; 4,277,154; 4,278,331; 4,278,318; 4,280,757; 4,278,319; 4,278,323; 4,278,888; 4,279,476; 4,279,477; 4,280,752;