Last month artforum.com reported that Amsterdam’s Vincent van Gogh Museum said that the drawings in the book Vincent van Gogh, the Fog of Arles: The Rediscovered Sketchbook (2016) were fake. The publisher, Le Seuil, along with the owner of the sketches, are threatening to sue the museum, Agence France-Presse reports.

The publisher said in a statement that it “intends to obtain compensation for the damage they have suffered as a result of an insidious and unfounded campaign” by the museum. The unidentified owner of the drawings “reserved the right to undertake any appropriate action to repair the damage caused by these claims that describe her as a forger,” said Franck Baille, an art expert who played a part in bringing the sketches to light.

The book’s author, Bogomila Welsh-Ovcharov, said the museum never properly examined the sketches—they based their claim on photographs of the works instead of the ten originals she brought to the museum for their perusal. The parties behind the book are also questioning why the museum should have final say on what is or isn’t an official Van Gogh. Felicity Strong, a researcher at the University of Melbourne, said, “The Van Gogh Museum has been wrong in the past. Their unveiling of a long-lost painting, Sunset at Montmajour, 1888, was examined by curators at the museum at least twice before they reassessed it in 2012 and [finally declared it to be authentic].”

The museum refuses to debate the matter publicly, as they are seeking answers directly from the publisher and think an open conversation would be useless. “We will need to have all the hard facts first,” said museum representatives. “We therefore call on the publisher and the author to provide a clear and open response to all our comments, to all the issues in need of clarification and to the questions raised. Until they have, we see no point in a scholarly debate and our contribution to the discussion ends here: we will no longer respond to further questions.”