Patents.
4,088,388; 4,152,699; 4,152,725; 4,152,729; 4,152,940; 4,153,334; 4,153,335; 4,153,336; 4,153,349; 4,154,049; 4,154,591; 4,154,592; 4,155,733; 4,156,556; 4,156,812; 4,157,477; 4,157,486; 4,157,861; 4,158,310; 4,157,906; 4,158,475; 4,157,860; 4,157,864; 4,158,325; 4,158,479; 4,158,503; 4,158,506.