Patents.
3,219,824; 3,160,696; 3,188,217; 3,188,218; 3,195,396; 3,200,018; 3,204,104; 3,205,087; 3,211,055; 3,213,281; 3,224,333; 3,229,566; 3,230,366; 3,230,379; 3,230,821; 3,234,380; 3,235,398; 3,235,731; 3,237,509; 3,239,368; 3,240,105; 3,241,438; 3,241,444; 3,242,336; 3,249,004; 3,271,179; 3,271,180; 3,272,917; 3,274,030; 3,274,440; 3,318,184; 3,320,014; 3,320,015; 3,320,016; 3,320,017; 3,321,264; 3,338,147; 3,349,680; 3,356,500; 3,356,846; 3,361,027; 3,363,503; 3,367,229; 3,367,231.