Tolong jelaskan mengenai Sumber sekunder dari Les XX

Autour de 1900: L'Art Belge (1884–1918). London: The Arts Council, 1965.

Block, Jane, Les XX and Belgian Avant-Gardism 1868–1894, Studies in Fine Arts: The Avant garde, Ann Arbor: UMI Research press, 1984.

Herbert, Robert. Georges Seurat, 1859–1891, New York: Metropolitan Museum of Art, 1991. .

Les XX, Bruxelles. Catalogue des dix expositions annuelles, Brussels: Centre international pour l'étude de XIXe siècle, 1981.

Stevens, Mary Anne and Hoozee, Robert (eds.), Impressionism to Symbolism: The Belgian Avant-Garde 1880–1900, exhib. cat. London: Royal Academy of Arts, London 7 July – 2 October 1994.