Cubism Ossip Zadkine as well as Jacques Lipchitz and Henri Laurens; and painters such as Louis Marcoussis, Roger de La Fresnaye, František Kupka, Diego Rivera, Léopold Survage, Auguste Herbin, André Lhote, Gino Severini (after 1916), María Blanchard (after 1916) and Georges Valmier (after 1918). More fundamentally, Christopher Green argues that Douglas Cooper's terms were "later undermined by interpretations of the work of Picasso, Braque, Gris and Léger that stress iconographic and ideological questions rather than methods of representation." John Berger identifies the essence of Cubism with the mechanical diagram. "The metaphorical model of Cubism is the diagram: The diagram being a
20th-century Western painting for that spiritual knowledge. Other major pioneers of early abstraction include Swedish painter Hilma af Klint, Russian painter Kazimir Malevich, and Swiss painter Paul Klee. Robert Delaunay was a French artist who is associated with Orphism, (reminiscent of a link between pure abstraction and cubism). His later works were more abstract, reminiscent of Paul Klee. His key contributions to abstract painting refer to his bold use of color, and a clear love of experimentation of both depth and tone. At the invitation of Kandinsky, Delaunay and his wife the artist Sonia Delaunay, joined The Blue Rider (Der Blaue Reiter), a