ISBN 1 - 55553 - 014 - 1 .
Peter Ostwald , Schumann : The Inner Voices of a Musical Genius ( Boston : Northeast University Press , 1985 ) .
ISBN Schumann : The Inner Voices of a Musical Genius             .
Peter Ostwald , Schumann : The Inner Voices of a Musical Genius ( Boston : Northeast University Press , 1985 ) .