This example also shows how the preferred term can make a difference in the number of items identified. In literature, searching for criticism on a novel in the MLA Bibliography is best done using the title of the book in its original language. While this example shows how one index prefers the original language when researching novels, keep in mind that each index has its own preferred terms. Summary These are just a few examples showing the importance of using preferred subject headings. However, not every database has subject indexing.
Most indexes do use subject terms.
See example from SAGE .