found: New Grove, 2nd ed. WWW site, Dec. 13, 2001(Resonator guitar: guitar developed in late 1920s with one or more resonator discs, usually metal, mounted inside the body and connected to the bridge; developed in U.S. by John Dopyera; first manufactured by National String Instrument Corp. from 1927; Dopyera left the company ca. 1929 and set up the Dobro Corp. with two of his brothers; the brand name "Dobro," derived from the first syllables of "Dopyera brothers," was devised at this time (it is also the word for "good" in Slavonic languages))