Patents.
4,744,634; 4,744,654; 4,747,649; 4,748,614; 4,749,262; 4,750,799; 4,750,809; 4,753,505; 4,758,060; 4,758,090; 4,758,092; 4,759,595; 4,759,613; 4,762,383; 4,762,394; 4,762,397; 4,762,399; 4,762,404; 4,763,990; 4,763,998; 4,764,001; 4,765,722; 4,765,736; 4,767,192.