Belonging to or characteristic of the French experimental writers' group calling itself OULIPO or OuLiPo (Ouvrior de Littérature Potentielle) in the 1960s and 1970s. The group's founders in 1960 included the lapsed surrealist writer Raymond Queneau and the mathematician François Le Lionnais, and they were joined by Jacques Roubaud (from 1966), Georges Perec (from 1967), and others, including some foreign members, notably the Italian author Italo Calvino (from 1973) and the American Harry Mathews, both then resident in Paris. The group's central purpose was to explore the literary possibilities of artificial constraints and mathematical combinations, for instance in the use of lipograms such as Perec's novel La Disparition (1969), or in Queneau's extraordinary sonnet sequence Cent mille milliards de poèmes (1961), in which the lines could be recombined in an enormous number of possible permutations. Among the other major works of Oulipian experiment is Perec's novel Vie mode d'emploi (1978; translated as Life: A User's Manual). The group's most important collective work was La littérature potentielle (1973). For an introductory anthology in English, consult Warren F. Motte (ed. and trans.), Oulipo: A Primer of Potential Literature (1986).