Patents.
3,190,177; 3,217,588; 3,217,589; 3,273,445; 3,320,849; 3,353,440; 3,397,935; 3,398,634; 3,404,279; 3,407,298; 3,411,840; 3,411,952; 3,412,278; 3,413,482; 3,413,567; 3,414,346; 3,414,354; 3,414,355; 3,414,356; 3,414,729;