Koszinowski, Ingrid. Otto Ritschl, 1885–1976: Retrospektive. Museum Wiesbaden and Von der Heydt-Museum, Wuppertal, Germany, 1997.

Mark Rothko: Works on Paper will ultimately document approximately 2,600 works from public and private collections worldwide. Cataloging is ongoing, and works and information will be added to the site during the coming years.