克諾克 Patrick De Brock 畫廊
現藏者於2007年購自上述來源
Museum of Fine Arts Bern, 'There is Desire Left (Knock, Knock)': 40 Years of Fine Arts from the Mondstudio Collection, 25 January - 27 April 2008 (another variant exhibited)
Julian Opie Portraits, Zurich, 2002, n.p (another variant illustrated)