Concrete art is an art movement with a strong emphasis on abstraction. The artist Theo van Doesburg, closely associated with the De Stijl art movement, coined the term "concrete art" as he in 1930 founded the group Art Concret and articulated its features in a manifesto titled "The Basis of Concrete Art", signed by four other artists of the group, including Otto G. Carlsund, Jean Hélion and Leon Tutundjian. The manifesto explained that the resultant art should be non-referential insofar as its components should not refer to, or allude to, the entities normally encountered in the natural, visible world. This is a distinction from abstraction generally. In a more general sense "abstract art" could and often does include the "abstraction of forms in nature". But "concrete art" was intended to