Patents.
3,711,199; 3,716,286; 3,716,287; 3,718,074; 3,720,779; 3,723,010; 3,724,943; 3,729,634; 3,731,265; 3,731,993; 3,739,093; 3,740,111; 3,752,556; 3,754,814; 3,756,683; 3,158,186; 3,764,979; 3,784,310; 3,784,377; 3,785,724; 3,786,366; 3,787,112; 3,788,745; 3,791,719; 3,791,720; 3,802,765; 3,803,510; 3,804,494; 3,804,496; 3,804,528; 3,804,531; 3,804,619; 3,805,186; 3,806,231; 3,806,237; 3,806,725; 3,806,871; 3,807,835; 3,807,836; 3,809,457; 3,810,042; 3,810,693; 3,811,095; 3,811,748; 3,811,749; 3,811,754; 3,813,158; 3,813,552; 3,813,611.