For articles, try the LION (Literature Online) database. You'll find a number of articles here on Brecht and his work, as well as other types of resources.
"Brecht was impressed by John Gay's The Beggar's Opera of 1728 and wrote his own musical version in German, Die Dreigroschenoper (The Threepenny Opera) in 1928. Like the original, it is set in London."
All Theater Is Revolutionary Theater by 
Artists in Exile: how refugees from twentieth-century war and revolution transformed the American performing arts by 
Bertolt Brecht's Dramatic Theory by 
Hitler's Exiles: personal stories of the flight from Nazi Germany to America by 