Patents.
4,884,874; 4,886,343; 4,884,874; 4,886,343; 4,902,108; 4,913,531; 4,925,276; 4,948,229; 4,964,684; 4,968,119; 4,968,120; 5,050,992; 5,051,571; 5,052,764; 5,052,765; 5,056,880; 5,056,901; 5,058,977; 5,059,027; 5,059,786; 5,061,025; 5,061,032; 5,062,094; 5,063,292; 5,063,586; 5,063,781; 5,064,259; 5,064,262; 5,067,782; 5,067,805; 5,069,532; 5,076,669; 5,080,490; 5,083,866; 5,090,795; 5,090,811; 5,092,342; 5,094,526; 5,102,222; 5,104,221; 5,104,224; 5,105,305; 5,106,193; 5,107,526; 5,108,183; 5,110,210; 5,112,121; 5,115,137; 5,118,181; 5,121,257; 5,121,978; 5,122,650; 5,125,743; 5,130,546; 5,131,023; 5,134,521; 5,134,523; 5,278,482.