Bart van der Leck, Study, (1916–17), Gouache and pencil on paper, The Museum of Modern Art, New York. https://dartabase.art/cite/moma/38256

Bart van der Leck, [Untitled], 1917, Gouache and pencil on paper, The Museum of Modern Art, New York. https://dartabase.art/cite/moma/34792