Patents.
3,645,604; 3,647,284; 3,657,981; 3,658,415; 3,658,419; 3,666,465; 3,674,338; 3,682,531; 3,702,397; 3,702,736; 3,704,066; 3,704,931; 3,704,933; 3,709,131; 3,709,586; 3,709,587; 3,709,588; 3,709,599; 3,709,600; 3,709,607; 3,709,683; 3,709,684; 3,710,013; 3,710,014; 3,709,689; 3,710,122; 3,710,127; 3,710,277; 3,710,697; 3,711,178; 3,711,187; 3,711,191; 3,711,200; 3,711,201; 3,711,208; 3,711,283; 3,711,637; 3,711,708; 3,711,786; 3,711,789; 3,711,790;