Since 1997, both the Association of Art Museum Directors (AAMD), and the American Association of Museums (AAM) have urged American museums to reaffirm their commitment to a series of standards governing provenance research. According to guidelines issued by these organizations, museums have been charged with identifying European paintings with incomplete or questionable provenance during the Nazi era, with particular attention to paintings that were created before 1946 and acquired after 1932, and that were, or could have changed hands, in continental Europe during this period.

Obtaining a complete provenance for a work of art from the time it left the artist to the time it entered a museum is a difficult and time-consuming task. Investigation into a painting's history of ownership includes physical examination of the work in question (particularly important are labels and inscriptions on the stretcher), consultation of object files and museum archives, auction and exhibition catalogues, monographs, publications on the activities of dealers and collectors, internet databases, dealer records, photographic and other archives, as well as correspondence with specialized scholars. Unlike title records kept on parcels of real estate, no centralized records exist for works of art. In fact, missing details about a change in ownership of art works (including the date and location of the transfer), are not uncommon. Sometimes works of art were bought and/or sold anonymously, or dealers who were active during and immediately after World War II no longer exist. In some cases dealers who collaborated in the looting had legitimate businesses prior to the Nazi era; in other cases the records of dealers or auction houses may be incomplete, or were lost or destroyed in the intervening years. Therefore, a gap in a painting's provenance during the Nazi era does not necessarily mean that a work of art was looted or stolen, but it does indicate that additional research is warranted.