In his letter to Theo, from the Hague, c. 11 July 1883 - original manuscript at Van Gogh Museum, location Amsterdam - inv. nos. b322 a-c V/1962, http://vangoghletters.org/vg/letters/let361/letter.html
At the exhibition 'Les cent chefs d'oeuvre' at Galerie Georges Petit - in Paris, 1883 there were 9 paintings of Troyon. Vincent had asked Theo in Paris to give him a description of the works at this exhibition. Vincent already appreciated Troyon's painting style, which he knew from his Paris' years at art-gallery Goupil where he worked
1880s, 1883