According to the assignment sheet, you are to find "An article (from a journal) or an essay (from a book) that analyzes the novel or short story that you read (minimum one argument source; preferably two)." To find an essay in a book, use either 1) the Library discovery system (as demonstrated), or 2) one or more of the many indexes listed in the boxes below. To find an article in a journal use 2) one or more of the many indexes listed in the boxes below.
Nonetheless, the indexes listed below will return much more of relevance. For example, this Subject search was run in the MLA International Bibliography. Note that it returns 19 articles and essays on J. R. R. Tolkien's "Leaf by niggle":
For a list of the many relevant indexes, see the boxes below.
For help FInding the Full Text, go to the bottom of this page.
SPU databases will link to SPU full-text quite automatically. Those on the open Web will not. So use the latter (Google Scholar only excepted) in conjunction with Finding the Full Text.
For more (non course-specific) help with the mechanics of searching both Primo (SPU Library + Summit) and WorldCat (Libraries Worldwide), see the document below: