Patents.
3,976,356; 3,993,963; 3,995,935; 3,995,937; 4,000,936; 3,997,241; 3,999,835; 3,999,836; 3,999,837; 4,009,932; 4,040,718; 4,060,328; 4,062,628; 4,070,111; 4,070,112; 4,076,422; 4,078,857; 4,080,047; 4,080,534; 4,082,425; 4,087,160; 4,093,339; 4,093,342; 4,093,343; 4,093,346; 4,094,583; 4,093,345; 4,094,586; 4,094,587; 4,097,124; 4,097,125; 4,099,831; 4,099,833; 4,099,834; 4,099,835; 4,099,844; 4,099,845; 4,099,846; 4,099,847; 4,099,872; 4,101,195; 4,101,220.