Patents.
4,201,222; 4,309,084; 4,309,108; 4,320,973; 4,325,637; 4,340,302; 4,341,470; 4,342,517; 4,343,182; 4,343,532; 4,345,475; 4,345,823; 4,345,833; 4,345,837; 4,345,840; 4,346,966; 4,347,000; 4,347,210; 4,347,437; 4,347,485; 4,347,486.