Patents.
3,227,873; 3,267,802; 3,347,616; 3,348,047; 3,349,665; 3,363,108; 3,366,789; 3,366,795; 3,413,467; 3,413,478; 3,415,589; 3,415,984; 3,418,478; 3,420,688; 3,424,512; 3,428,398; 3,437,403; 3,437,816; 3,439,969; 3,439,975; 3,439,976; 3,437,824; 3,439,985; 3,440,046; 3,441,338; 3,442,567; 3,442,573; 3,443,102; 3,443,862; 3,443,863; 3,443,864; 3,445,154; 3,446,558; 3,443,853; 3,448,282; 3,447,854; 3,446,967; 3,447,858; 3,447,861; 3,447,876; 3,448,283.