 Cassirer first established a market for Van Gogh, and then, with the assistance of Johanna van Gogh-Bonger, controlled market prices.In 1906 Bruno Cassirer published a small volume of selected letters of Vincent's to Theo, translated into German.However, Johanna was keen to maintain her independence, and contributed important loans to Roger Fry's 1910 London exhibition, as well as to the important Sonderbund exhibition of 1912 in Cologne, where Van Gogh was introduced to visitors as "the father to us all".