About Ruimtecircus I, 1956-1961 at Rijksmuseum Amsterdam.
Documentation
Pages
Call the witness
Video with Tom McDonough (art historian, United States) on Campo nomadi: Constant’s Design for a Gypsy Camp.
Constant (Nieuwenhuys) Amsterdam 1920 – 2005 Utrecht
Short history on Constant and Cobra with comments of Jan Elburg.
Gemeentemuseum
The New Babylon project, part of the museum's masterpieces with some links to secondary materials in Dutch.