An expository essay allows the writer to present information arguing an idea through comparison and contrast, definition, causal analysis or illustration. Because such papers often involve research, writers must apply an appropriate documentation format, such as MLA style from the Modern Language Association, to properly convey the sources for borrowed information.
The MLA established formatting guidelines to create consistency in papers and publications within disciplines. Writers indicate sources of outside information through unobtrusive in-text citations and a bibliography list that allows readers to find more information. Properly citing borrowed words and ideas lends credibility to a writer's work. Papers written in composition courses, which often use expository modes of development, as well as those with topics in English and foreign languages, literature, literary criticism or theory and cultural studies -- any of which might be used with expository modes of development -- typically require MLA style.
According to the "MLA Handbook for Writers of Research Papers," MLA style does not use title pages for an expository essay or research paper. Instead, put your name, instructor's name, the course number, the title and the due date for the paper in the upper-left corner of the first page. After a space, type the title of the essay and center it. Underlining, italics and quotation marks indicate that a title has been published, so use such formatting only to indicate when your title includes the name of a published piece such as the titles of two poems you might be contrasting. Use a header that gives your last name followed by the page number of the manuscript on the upper-right corner of each page. Double-space everything in MLA style.
If you take information from an outside source word-for-word such as a line from a poem you are writing a literary criticism of, put quotation marks around that language and include a citation to show the source. The citation gives the author's last name, a space and the page number -- with no punctuation in between -- inside parentheses. Place the period after the citation. Also cite ideas you borrow from outside sources, such as another writer's interpretation of a poem's theme, using the same format. You may also place the author in a signal phrase with the page number at the end. To cite works that do not list an author, use the title of the piece, putting quotation marks around the title of an article or short work and italicizing a book or longer piece. Leave page numbers off for websites that do not include page or paragraph numbers.
The rest of the bibliographical information for your sources appears on the Works Cited page at the end of your expository paper. Alphabetize the sources by the author's last name and use a hanging indent. Include authors' first names followed by the title of the piece and then publishing information, such as the city, publisher and date for books and the magazine or journal name, date and page numbers for periodicals. At the end of each entry, type "Print" or "Web" to indicate the publication medium. Include all the works you cited in your paper, not just the primary pieces your exposition focused on.