Provenance
The Getty Provenance Index databases currently contain 1.5 million records taken from source material such as archival inventories, auction catalogs, and dealer stock books. This vast collection of digital records is expanded and enriched on a regular basis. The quantity and scope of research material that is available varies by region, period, and type of document. (Description taken from the website)
The AAM guide to provenance research, Nancy H. Yeide, Konstantin Akinsha, Amy L. Walsh. Washington, D.C. : American Association of Museums, 2001, 304 p., http://id.lib.harvard.edu/aleph/008732171/catalog