František Kupka, Replica of Fugue in Two Colors: Amorpha, 1912, (1946), Gouache, ink, and pencil on paper, The Museum of Modern Art, New York. https://dartabase.art/cite/moma/34761

František Kupka, Replica (1946) of Vertical Planes, (1946), Watercolor, gouache, and pencil on paper, The Museum of Modern Art, New York. https://dartabase.art/cite/moma/34788