A book titled Vincent Van Gogh, the Fog of Arles: The Rediscovered Sketchbook, to be published by Le Seuil this month, contains sixty-five drawings that have been called imitations by the Van Gogh Museum in Amsterdam, according to Le Monde.

The contested drawings are made in ink on an accounts book from a hotel in Arles where the painter is believed to have stayed. The book of sketches, which hails from a private collection, contains mostly landscapes of the Arles region as well as a few portraits, including one of Gauguin, supposedly made between 1888 and 1890.

The Van Gogh Museum based its decision regarding the authenticity of the drawings on “years of research on Van Gogh’s drawings in the museum’s collection and other places.” Experts who examined the drawings noticed certain inconsistencies, such as the fact that brown ink has never been found in drawings made by the artist between 1888 and 1890. The Van Gogh Museum has some five hundred Van Gogh drawings and four of his sketchbooks in its collection.