Patents.
4,717,250; 4,725,143; 4,746,192; 4,747,650; 4,758,071; 4,758,081; 4,747,671; 4,755,029; 4,758,070; 4,758,085; 4,761,054; 4,767,169; 4,767,199; 4,767,201; 4,767,206; 4,767,196; 4,767,198; 4,768,513; 4,768,846; 4,768,852; 4,768,866; 4,768,867; 4,768,868; 4,768,881; 4,770,477; 4,770,478; 4,770,508; 4,770,510; 4,770,512; 4,770,513; 4,770,514; 4,770,516; 4,770,517; 4,772,101; 4,772,104; 4,772,105; 4,772,106; 4,772,107; 4,772,108; 4,773,745; 4,773,746; 4,773,756; 4,775,204; 4,775,223; 4,775,228; 4,776,654; 4,776,679; 4,776,680; 4,776,681; 4,776,682; 4,778,264; 4,778,984;