Patents.
4,669,088; 4,670,883; 4,672,619; 4,674,881; 4,676,643; 4,677,641; 4,681,446; 4,685,107; 4,687,331; 4,691,323; 4,695,160; 4,697,876; 4,697,888; 4,698,823; 4,699,005; 4,702,550; 4,702,600; 4,702,601; 4,703,182; 4,705,398; 4,705,952; 4,708,421; 4,708,442; 4,708,443; 4,708,444; 4,708,445; 4,709,997; 4,709,998; 4,710,030; 4,711,126; 4,711,515; 4,711,516; 4,712,886; 4,715,672.