Patents.
3,462,224; 3,464,770; 3,468,600; 3,469,102; 3,470,374; 3,486,808; 3,488,105; 3,489,486; 3,496,355; 3,504,960; 3,507,556; 3,507,565; 3,515,461; 3,515,489; 3,516,730; 3,518,010; 3,519,352; 3,521,947; 3,522,986; 3,523,160; 3,523,721; 3,523,732; 3,523,738; 3,524,694; 3,524,695; 3,524,696; 3,524,697; 3,524,698; 3,524,699; 3,524,700; 3,524,710; 3,524,928; 3,524,988; 3,525,562; 3,525,572; 3,525,807; 3,526,777; 3,527,523; 3,527,526; 3,528,727; 3,528,737; 3,528,740; 3,528,743; 3,529,161; 3,529,527; 3,529,887; 3,529,888; 3,529,892; 3,529,894; 3,529,895; 3,530,324; 3,530,779; 3,531,211; 3,532,414; 3,532,415; 3,532,416; 3,532,425; 3,533,675; 3,533,677; 3,533,678; 3,533,679; 3,533,690; 3,533,697; 3,535,016; 3,535,023; 3,535,025; 3,535,044; 3,535,993; 3,536,379; 3,536,917; 3,536,919; 3,536,948; 3,539,251; 3,539,262; 3,539,811; 3,539,814.