Not sure if a website is an appropriate source to cite? What does it mean to be credible, anyways? Check out this video for an overview of source evaluation.
"Founded in 1989, and online since 1995, artnet is the leading resource for the international art market, and the principal platform for art auctions on the Internet. We offer a wide range of art market resources, providing a place for people in the art world to buy, sell, and research Fine Art, Design, and Decorative Art."
9.7 million auction records from 1922 to the present day. Belmont does not have access to the paid portion of this website, but it's still a useful tool for researching an artwork's provenance.
"A biographical and methodological database intended as a beginning point to learning the background of major art historians of western art history. A free, copyrighted, scholarly database for the use of researchers, students and the public."