slightly out of topic, but still crossed: there is a database Art Loss Register (
www.artloss.com), which contains lists of stolen items, even those who were expropriating during World War II. And it was not a few cases where the current owners had to agree (or return the work, or return a portion of its cost) to the descendants of the owners. Is interesting that the descendants themselves did not expect that they belong to such a value, yet it has not been accessed auction houses. The fact that the auction houses to check on the basis of the important lots, and, if they find them in this basis, notify the rightful owners. The situation for the current owners, of course, not a recipe, but alas. Therefore, when buying expensive works quite appropriate to test them on that basis. The cost of one request - $ 50.