Patents.
3,185,020; 3,211,049; 3,211,910; 3,214,596; 3,227,034; 3,229,568; 3,232,165; 3,239,660; 3,240,111; 3,268,719; 3,365,577; 3,393,321; 3,393,600; 3,394,259; 3,398,279; 3,398,281; 3,405,276; 3,406,356; 3,408,133; 3,409,351; 3,410,642; 3,417,346; 3,405,276; 3,417,246; 3,420,594; 3,418,476; 3,420,602; 3,421,003; 3,421,807; 3,421,808; 3,421,810; 3,422,301; 3,423,149; 3,424,516; 3,424,518; 3,430,160; 3,200,701; 3,427,104; 3,428,386; 3,428,389; 3,428,390; 3,428,391; 3,429,637; 3,429,997; 3,430,041; 3,430,045; 3,430,047; 3,424,520; 3,424,521; 3,424,522; 3,424,523; 3,425,770; 3,426,201; 3.427,089; 3,427,092.