May 22, or 23, 1890. Letter from Vincent van Gogh to Theo van Gogh, Auvers-sur-Oise, 25 May 1890 [letter 637]: Please tell me sometime, which is the picture that Mlle. Bock has bought? I must write to her brother to thank them and then I shall suggest exchanging two of my studies for one of each of theirs. I have a drawing of an old vine, from which I intend to make a canvas of size 30, and a study of pink chestnuts and one of white chestnuts. But if circumstances allow it, I hope to work a little at the figure. Some pictures present themselves vaguely to my mind, which it will take time to get clear, but that will come bit by bit. If I had not been ill, I should have written to Bock and Isaacson long ago. (http://www.tfsimon.com/auvers-sur-oise.html)