Patents.
3,703,330; 3,848,964; 3,848,965; 3,848,967; 3,848,968; 3,848,969; 3,848,971; 3,849,738; 3,848,972; 3,850,502; 3,850,507; 3,850,509; 3,851,318; 3,851,952; 3,851,953; 3,853,387; 3,854,793; 3,856,385; 3,856,386; 3,858,124; 3,858,201.