Patents.
3,406,293; 3,505,613; 3,506,927; 3,516,009; 3,516,012; 3,519,323; 3,519,324; 3,521,178; 3,522,979; 3,523,734; 3,524,056; 3,529,083; 3,529,152; 3,529,159; 3,529,883; 3,529,896; 3,531,204; 3,531,207; 3,532,406; 3,532,407; 3,532,431; 3,533,674; 3,534,291; 3,535,013; 3,537,795; 3,537,796; 3,538,452; 3,539,242; 3,539,804; 3,543,180; 3,543,181; 3,543,183; 3,544,191; 3,544,193; 3,544,194; 3,544,200; 3,544,201; 3,544,202; 3,545,835; 3,545,836; 3,546,460; 3,546,469; 3,547,517; 3,547,526; 3,547,549; 3,548,192; 3,548,194; 3,549,260; 3,550,039; 3,551,017; 3,551,018; 3,551,024; 3,551,027; 3,551,028; 3,551,030; 3,551,031; 3,551,053; 3,551,054; 3,552,829; 3,552,830; 3,552,831; 3,552,832; 3,554,632; 3,556,631; 3,556,640; 3,556,659; 3,558,207; 3,558,213; 3,558,230; 3,560,091; 3,561,838; 3,562,522; 3,562,529; 3,562,667.