Complex sentence: A Wildenstein Index Number refers to an item in a numerical system published in catalogues by Daniel Wildenstein, a distinguished scholar of Impressionism, who published catalogues raisonnés of artists such as Claude Monet, Edouard Manet and Paul Gauguin through his family business, Wildenstein & Company.
Split into simpler sentences: A Wildenstein Index Number refers to an item in a numerical system published in catalogues by Daniel Wildenstein, who was a distinguished scholar of Impressionism. As a scholar he published catalogues raisonnés of artists such as Claude Monet, Edouard Manet and Paul Gauguin through his family business, Wildenstein & Company.