The Art Newspaper reports that a "new authentication dispute has cropped up around the work of the Canadian-born American abstract painter Agnes Martin, whose minimalist paintings are currently the focus of an exhibition at the Guggenheim Museum in New York (until 11 January). The Mayor Gallery of London filed a lawsuit in New York state court on October 17 against the company behind the Agnes Martin catalogue raisonné and the members of its authentication committee."

Thirteen works brought by the gallery's clients to the committee were rejected, thus rendering them "worthless" on the market, according to court papers.