Patents.
4,856,876; 5,035,481; 5,037,203; 5,037,204; 5,046,803; 5,046,817; 5,048,935 5,048,936; 5,050,968; 5,050,990; 5,070,241; 5,071,231; 5,076,662 5,078,502; 5,080,483; 5,080,487; 5,080,488; 5,088,824; 5,089,711; 5,090,812 5,096,279; 5,096,297; 5,100,218; 5,100,230; 5,100,235; 5,100,236; 5,101,294 5,104,209; 5,105,287; 5,113,402; 5,106,174.