This answer is incorrect.  The word "by" before the author's name should only be used on the catalog record if it appears that way on the item itself.  For example, if the title page of a book says, The Grapes of Wrath and John Steinbeck's name is listed below without the word "by," then the catalog record should not say, The grapes of wrath / by John Steinbeck.  It should simply say The grapes of wrath / John Steinbeck.  Please go back and try again.