Patents.
3,153,978; 3,166,625; 3,169,186; 3,311,748; 3,313,205; 3,316,799; 3,317,328; 3,320,852; 3,321,629; 3,321,630; 3,323,407; 3,323,917; 3,324,294; 3,325,647; 3,331,963; 3,331,982; 3,334,226; 3,339,109; 3,340,064; 3,342,995; 3,348,045; 3,348,978; 3,351,758; 3,359,102; 3,362,285; 3,364,374; 3,364,376; 3,365,581; 3,366,736; 3,377,912; 3,380,792; 3,381,136; 3,383,150; 3,385,160; 3,385,162; 3,385,925; 3,387,140; 3,387,531; 3,389,293; 3,393,337; 3,391,599; 3,393,958; 3,394,975; 3,395,962; 3,397,024.