Referencing systems are supposed to help readers identify the sources used in a book, article or essay. For the most part they achieve this, but there are some situations that cause problems.
If you’ve cited several sources by the same author from the same year, for example, it can be hard to tell them apart in many citation systems. To ensure that sources are referenced clearly in your written work, then, you may need to take a different approach.
Author–Date Citations
When a system gives full source information in footnotes (e.g. Chicago or MHRA style), citing several sources by a single author from the same year isn’t usually a problem. The footnotes will provide enough information to make it clear which source you’re citing each time. However, when a referencing system uses parenthetical author–date citations, things get tricky.
This kind of referencing doesn’t let us tell sources by the same author from the same year apart, since all citations would use the same name and date! As such, most parenthetical referencing systems (e.g. Harvard and APA) use a letter after the year in these cases (bold added for emphasis):
An embarrassing name can negatively impact social interactions (Butz, 2002a). Research also suggests that it has a negative influence on professional achievement (Butz, 2002b).
Here, for example, we have two sources by the unfortunately-named (and thankfully fictional) Seymour Butz. Both are from 2002, so we need to add a letter after each one to tell them apart. These letters would then be added to the corresponding reference list entries:
Butz, S. (2002a). Me and my name. Simpson and Co. Publishing.
Butz, S. (2002b). Nomenclature and professional success. The Journal of Naughty Surnames, 34(2), pp. 210-224.
The order of entries in the reference list will depend on the system used. In the above, since we have used APA rules, they’re listed alphabetically by the title of the source.
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MLA Referencing
MLA citations do not include a year of publication, so the approach for citing multiple sources by the same author is a little different. With MLA, you should include the title when citing more than one source by the same person:
Butz says that an embarrassing name can negatively impact social interaction (Me and My Name 44). His research also suggests that it has a negative influence on professional achievement (‘Nomenclature and Professional Success’ 219).
If the author is not named in the text, however, include it in citations:
This has affected many people (Butz, Me and My Name 120).
Sources are then listed in full on the ‘Works Cited’ page, using three hyphens in place of the author’s name(s) for each entry after the first:
Butz, Seyour. Me and My Name. Simpson and Co. Publishing, 2002.
– – -. ‘Nomenclature and Professional Success’. The Journal of Naughty Surnames, vol. 34, no. 2, 2002, pp. 210-24.
These rules actually apply in MLA referencing whenever you cite more than one source by the same author, not just when citing multiple sources by one author from the same year.