Photo, 1957 Yves Klein in front of his Sponge Sculpture at the exhibition "Monochrome Propositions of Yves Klein" Gallery One, London
Article, 1961, Roland F. Pease Jr. Testimonial of Roland F. Pease Jr. on the blue monochromes seen at the Leo Castelli exhibition, 1961
Photo, january 14th 1961 Yves Klein surrounded by Sponge Sculptures during the exhibition "Monochrome und Feuer", Museum Haus Lange