Patents.
5,094,534; 5,096,293; 5,105,293; 5,105,295; 5,106,184; 5,110,204; 5,110,208; 5,111,322; 5,080,469; 5,110,217; 5,116,127; 5,118,189; 5,121,985; 5,132,976; 5,132,983; 5,133,600; 5,137,356; 5,137,358; 5,137,359; 5,137,360; 5,140,600; 5,141,315; 5,157,462.