Cubism the 1950s and 1960s, especially by Clement Greenberg. Contemporary views of Cubism are complex, formed to some extent in response to the "Salle 41" Cubists, whose methods were too distinct from those of Picasso and Braque to be considered merely secondary to them. Alternative interpretations of Cubism have therefore developed. Wider views of Cubism include artists who were later associated with the "Salle 41" artists, e.g., Francis Picabia; the brothers Jacques Villon, Raymond Duchamp-Villon and Marcel Duchamp, who beginning in late 1911 formed the core of the Section d'Or (or the Puteaux Group); the sculptors Alexander Archipenko, Joseph Csaky and
Czech Cubism secessionist designers such as Otto Wagner and Jan Kotěra. Architects such as Josef Chochol and Pavel Janák devised spiritualist philosophies of design and a dynamic ideal of planar form derived from cubist art. As Cubism spread across the European continent in the early 20th century, its greatest impact can be seen today in the Czech Republic. Pyramid and crystal forms were one of the signature principles seen in Czech Cubism which was incorporated in architecture, furniture, and applied arts. The Museum of Decorative Arts in Prague (UPM) uses the House of the Black Madonna as a permanent exhibition space for