The Traité de zoologie des éditions Masson, complete title Traité de zoologie, anatomie, systématique, biologie popularly known as le Grassé is a 52 volume synthesis of Zoology published between 1948 and 1979 originally under the direction of Pierre-Paul Grassé. A new edition commenced in 1980. The books were not published in order, and some promised parts are yet to appear. The books are written in the French language. Source: Wikipedia (en)