Patents.
3,794,426; 3,799,642; 3,807,828; 3,807,829; 3,809,873; 3,813,685; 3,814,503; 3,818,129; 3,818,374; 3,818,375; 3,831,105; 3,831,106; 3,831,107; 3,831,108; 3,834,809; 3,836,224; 3,837,725; 3,837,726; 3,838,903; 3,838,904; 3,843,225; 3,843,260; 3,847,465; 3,848,228; 3,849,001; 3,851,948; 3,853,384; 3,855,470; 3,856,378; 3,894,787; 3,894,788; 3,897,995; 3,899,240; 3,899,253; 3,899,254; 3,900,246; 3,901,582; 3,901,584; 3,902,061; 3,902,782; 3,902,790; 3,904,268; 3,905,019; 3,907,430; 3,909,134; 3,909,749; 3,910,680; 3,910,681 3,910,691.