Patents.
3,775,602; 3,885,856; 3,891,976; 3,892,465; 3,920,312; 3,920,313; 3,920,982; 3,922,062; 3,922,089; 3,922,064; 3,922,092; 3,923,373; 3,923,375; 3,923,376; 3,924,063; 3,924,927; 3,927,253; 3,927,385; 3,930,714; 3,930,728; 3,930,729; 3,930,730; 3,932,745; 3,982,487; B398,551.