The International Foundation for Art Research maintains an online catalog of catalogues raisonnés. Use it to find books (catalogues raisonnés) that list all known works by your artist (e.g., Mary Cassatt).
Before attempting to find books and articles related to your work of art, first build your knowledge about the artist who created your object and the style/period associated with it by consulting reference works for background information.
Artists of the World: Bio-Bibliographical Index A-Z (Allgemeines Künstlerlexikon)
Symbols and Allegories in Art
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Medieval Iconography: A Research Guide
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Church, Monastery, Cathedral: A Guide to the Symbolism of the Christian Tradition
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Library of Congress Subject Headings (LCSH):
Artist as subject: