In English
Arthur Elson: Modern Composers of Europe (Boston, 1905).
L. Gilman: Phases of Modern Music (New York, 1904).
James Huneker: Mezzotints in Modern Music (New York, 1899).
A. E. H. Krebhiel: The Pianoforte and its Music (New York, 1911).
Daniel Gregory Mason: From Grieg to Brahms (1903).
In German
Dagmar Gade: Niels W. Gade (Notes and Letters), (Basle, 1894).
Walter Niemann: Die Musik Skandinaviens (Leipzig, 1906).
Walter Niemann: Die moderne Klaviermusik in Skandinavien. Die Musik, vol. 14, No. 5, p. 195.