Patents.
3,704,932; 3,706,495; 3,708,222; 3,796,493; 3,796,498; 3,814,505; 3,814,510; 3,817,599; 3,816,735; 3,817,600; 3,817,602; 3,818,125; 3,819,253; 3,819,256; 3,820,876; 3,820,897; 3,821,466; 3,821,551; 3,822,087; 3,822,931; 3,825,346; 3,826,992; 3,827,062; 3,827,781; 3,827,786; 3,827,793; 3,828,187; 3,829,198; 3,830,558; 3,830,559; 3,830,571; 3,832,028; 3,832,029; 3,832,030; 3,833,284; 3,833,286; 3,833,290; 3,833,810.