Patents.
3,648,056; 3,655,265; 3,683,770; 3,684,379; 3,685,906; 3,687,515; 3,692,388; 3,688,145; 3,695,745; 3,698,792; 3,699,339; 3,699,375; 3,700,314; 3,700,897; 3,702,930; 3,703,328; 3,703,329; 3,703,331; 3,703,660; 3,704,053; 3,704,056; 3,704,061; 3,704,127; 3,704,371; 3,704,936; 3,704,998; 3,705,757; 3,705,759; 3,707,322; 3,707,323; 3,707,324; 3,707,325; 3,708,220.