Patents.
3,771,124; 3,771,129; 3,773,401; 3,776,727; 3,779,631; 3,900,804; 3,903,483; 3,904,986; 3,906,397; 3,906,398; 3,911,276; 3,911,375; 3,911,376; 3,913,033; 3,920,315; 3,921,030; 3,921,136; 3,921,158; 3,922,060; 3,922,071; 3,922,072; 3,922,485; 3,922,524; 3,922,549; 3,923,369; 3,923,382; 3,924,925; 3,924,933; 3,924,934; 3,925,793; 3,926,503; 3,927,254; 3,927,933; 3,930,162; 3,931,515; 3,932,024.