Patents.
4,718,406; 4,721,372; 4,721,386; 4,725,111; 4,723,250; 4,723,843; 4,725,130; 4,725,142; 4,726,665; 4,726,666; 4,726,667; 4,726,668; 4,726,669; 4,728,165; 4,728,168; 4,728,179; 4,728,191; 4,729,632; 4,729,643; 4,730,105; 4,730,327; 4,730,906; 4,730,907; 4,730,908; 4,730,912; 4,732,448; 4,732,459; 4,733,926; 4,733,937; 4,733,964; 4,734,911; 4,735,476; 4,735,484; 4,735,485; 4,735,486.