APA style was created by the American Psychological Association, and it is used as the standard style in education, social and behavioral sciences. Developed by the Modern Language Association, MLA style is widely used in the humanities and literature writings. The Note and Bibliography (NB) system most commonly referred to as the Chicago referencing style is widely used in arts and humanities. On the other end, the Harvard referencing style is used in scientific writings to strengthen and clarify points borrowed from outside sources.
Attribution of sources inside the paper differs across the main styles. In APA style, an in-text citation includes the author’s last name and the year of publication, while in MLA, it includes the authorship and the exact page number from where the information was quoted. In Harvard style, in-text references should include the last name of the author and the year of the work. Documents formatted in Chicago style often includes a note -- footnote or endnote -- each time a source is used. A footnote is used each time a source is referenced, whether through a direct quote or a summary. Footnotes appear at the end of the paper on which the source is used, and endnotes will be added at the end of each chapter or sometimes at the end of the complete document.
The difference between a paper written in APA style and one written in either MLA or Chicago style is obviously visible to a reader almost immediately. A paper written in APA style will always contain a title page, while those written in MLA or Chicago will only have a title page if required by the instructor or otherwise requested. Even though the main body of documents formatted in MLA, APA and Harvard will look very similar, the two latter styles require the inclusion of an abstract or summary of the paper. In a Chicago or Harvard paper, the full list of references is found on the bibliography page, while the APA and MLA will include a “References” and “Work Cited” page, respectively.
Inclusion of Visual Aids
Harvard, Chicago and APA referencing styles makes specific guidelines on citing tables, figures, diagrams and other visual aids, where MLA does not. In an APA paper, graphical representations such as work plan and research questionnaires are included as appendices at the end of the document. In Harvard and Chicago, when reproducing selected data, or copying graphical elements from an outside source, a reference must be made to the source. In Harvard style, tables and figures are identified by location -- “below” -- rather than by numbers --“in figure 2”-- as in the case of Chicago referencing style.