“…The extension of Theorem 1 in various directions has been an active topic of research since its original publication. One major area of research has been the problem of understanding systematically what happens when the open set condition is removed (such as in [2,14,28,29,37,43,46,48]) and this line of research has focused especially on the dimensions of the resulting measures as opposed to the resulting sets. A second major direction of extension of Theorem 1 is that in which the transformations T i are allowed to be arbitrary affine contractions instead of similitudes: this line of research dates back to the work of Bedford, McMullen and Falconer in the 1980s [7,20,38] and has been particularly active within the last few years (see for example [4,5,6,11,17,22,25,35,44]).…”