French scholar Marc Restellini has braved death threats over his efforts to authenticate works by the Italian artist Amedeo Modigliani.

Now, in the wake of the record-smashing $170.4-million sale of one of the artist’s nudes at Christie’s New York in May, Restellini is back after having previously abandoned an effort to compile a catalogue raisonné, or exhaustive inventory, of Modigliani’s paintings, reports the Art Newspaper. His Institut Restellini will publish one online by year’s end, says the paper, though he had previously been threatened for declining to record certain works in his publication, which could damage their values, reported the New York Times in 2014.