Patents.
4,410,785; 4,411,487; 4,414,166; 4,414,556; 4,415,794; 4,417,123; 4,424,435; 4,430,548; 4,451,730; 4,456,339; 4,458,994; 4,462,095; 4,466,088; 4,467,168; 4,470,701; 4,473,297; 4,473,735; 4,482,249; 4,475,027; 4,475,199; 4,475,793; 4,487,483; 4,476,214; 4,477,187; 4,477,188; 4,479,701; 4,479,715; 4,483,617; 4,485,473; 4,487,472; 4,487,476; 4,488,041; 4,488,039; 4,458,980; 4,491,394; 4,491,395; 4,493,217; 4,482,803; 4,493,536; 4,494,819; 4,494,828; 4,494,829; 4,497,534; 4,496,223; 4,497,546; 4,497,547; 4,498,729; 4,498,741; 4,482,803; 4,493,536; 4,494,819; 4,494,828; 4,494,829; 4,497,534; 4,496,223; 4,497,546; 4,497,547; 4,498,729; 4,498,741; 4,483,617; 4,485,473; 4,487,472; 4,487,476; 4,488,041; 4,488,039; 4,458,980; 4,491,394; 4,491,395; 4,493,217.