Patents.
4,886,332; 4,886,339; 4,907,846; 4,925,259; 4,925,268; 4,927,269; 4,929,040; 4,929,052; 4,929,071; 4,929,083; 4,931,634; 4,931,635; 4,935,625; 4,934,821; 4,936,642; 4,936,645; 4,936,665; 4,936,644.