. . . "New York, 1919-1921"@en . . "Relating to negotiations between the Symphony Society and the Musical Mutual Protective Union, with letters and documents signed by Harry Harkness Flagler, Clarence Mackay, George Engles, Walter Damrosch, and others."@en . . . . . . . . "1919 03 31." . . . . "Musical Mutual Protective Union." . .