Auctions and auction records and data are vital tools in art historical research as well as in the study of art business for many reasons. They not only establish the value of works of art in a given time, they also provide vital data on the history of collecting, provenance, and the changing tastes of our society.
Among the resources available to MA students at the Sotheby's Institute of Art, New York Library are the last 5 years of physical auction catalogues from Sotheby's, Christie's, and Phillips, select catalogues of important sales going back to the 1960s, access to subscription auction sales databases (Artnet, Art Price, Invaluable, ArtBnk), reference sources such as Benezit and this guide to their use, as well as free recommended free resources such as the searchable databases on the websites of the major auction houses.
Always remember that SIA-NY librarians are always available to answer any questions you might have and to provide further instruction in the use of these (and all other) resources.