Patents.
3,211,048; 3,227,877; 3,271,578; 3,287,560; 3,288,017; 3,405,372; 3,406,354; 3,407,362; 3,409,345; 3,411,105; 3,423,147; 3,423,686; 3,424,997; 3,426,286; 3,426,293; 3,427,565; 3,427,566; 3,431,410; 3,432,219; 3,432,220; 3,432,223; 3,433,552; 3,433,554; 3,433,958; 3,433,959; 3,437,804; 3,437,811; 3,437,954; 3,438,712; 3,438,713; 3,439,164; 3,439,968; 3,439,972; 3,441,348; 3,442,591; 3,443,089; 3,443,090; 3,443,103; 3,443,869; 3,443,872; 3,444,383; 3,445,153; 3,445,668; 3,446,961; 3,446,547; 3,447,859; 3,447,873.