To search for critical works on Harlem Duet by Djanet Sears, try a keyword search:
harlem duet djanet sears
or a subject search using this format:
Sears, Djanet -- Criticism and interpretation
MLA is the best place to search for articles and book chapters on any topic related to literary criticism. With MLA you do not need to add the search term "criticism". Try a simple keyword search, for example:
Jane Eyre and disability
retrieves critical articles on the treatment of disability in Jane Eyre.
Other sources to try: