Patents.
3,653,738; 3,661,065; 3,685,883; 3,694,055; 3,700,308; 3,702,214; 3,704,934; 3,704,997; 3,783,403; 3,783,404; 3,783,406; 3,783,407; 3,792,918; 3,793,595; 3,794,431; 3,800,243; 3,801,928; 3,794,835; 3,798,568; 3,798,569; 3,798,570.