Patents.
5,044,727; 5,116,111; 5,120,940; 5,139,331; 5,133,599; 5,139,335; 5,142,417; 5,142,561; 5,143,435; 5,144,476; 5,144,497; 5,146,076; 5,146,080; 5,146,917; 5,149,949; 5,149,970; 5,150,172; 5,150,966; 5,151,585; 5,151,586; 5,151,592; 5,151,748; 5,151,820; 5,151,823; 5,151,826; 5,152,787; 5,152,788; 5,153,776; 5,155,616; 5,155,633; 5,157,258; 5,157,458; 5,157,460; 5,157,503; 5,157,532; 5,159,493; 5,159,496; 5,160,848; 5,161,059; 5,161,063; 5,162,949.