Patents.
3,940,608; 3,941,474; 3,941,927; 3,942,866; 4,067,651; 4,109,995; 4,113,374; 4,116,531; 4,119,362; 4,120,581; 4,126,783; 4,126,876; 4,127,771; 4,135,096; 4,152,824; 4,153,038; 4,153,039; 4,153,041; 4,153,474; 4,154,219; 4,155,371; 4,157,470; 4,162,119; 4,162,397; 4,162,399; 4,165,154; 4,165,914; 4,165,915; 4,165,916; 4,165,936; 4,165,937; 4,165,938; 4,166,254; 4,166,342; 4,166,668; 4,166,670; 4,166,671; 4,166,672; 4,166,674; 4,166,697; 4,166,932; 4,166,954; 4,167,337; 4,168,106; 4,168,110; 4,168,126; 4,168,429; 4,168,430; 4,168,435; 4,168,887; 4,168,890; 4,169,976; l4,171,154; 4,171,155; 4,171,890; 4,171,910; 4,172,222.