Library of Congress subject headings for exhibitions usually look like this in our online catalog:
Krasner, Lee, 1908-1984--Exhibitions.
Painting, Modern--20th century--Exhibitions
Folk art--Exhibitions.
You can also search by museum
Museum of Modern Art (New York, N.Y.)
Tate Gallery, London
Some other useful art key terms are "retrospective" and "catalogue raisonne"