 In 1956 this first volume on collectors' marks was followed by a Supplément.In 1922 he was commissioned to compile the inventory catalogue of Dutch and Flemish drawings in the Musée du Louvre.The first volume appeared in 1927, the series eventually comprising nine volumes cataloguing drawings of the Northern schools not only from the Louvre's collection but also in other collections in Paris, including the Petit Palais (the collection of Eugène Dutuit), the Bibliothèque Nationale, and the École des Beaux-Arts.