Most students understand that secondary sources are not preferred and should only be used when a primary source is not available. However, there is often a great deal of confusion as to what constitutes a secondary source and, more importantly, how to correctly cite one when it is used.
The reason for the confusion is because the term secondary source is a relative term, specifically, it’s relative to the primary source.
A primary source is any source with firsthand knowledge of the information being discussed. This could be letters and personal accounts from those who witnessed an event, it could be a research paper from someone who performed an experiment, a newspaper article from the time the event took place, a government report analyzing the event or a even a photograph from a moment of history.
Secondary sources are simply sources that use primary sources to discuss or interpret what the primary sources are commenting upon. These include everything from biographies, history books, news reports from after the event and even textbooks.
In short, where a primary source has direct knowledge of an event or an area of study, a secondary source tries to build upon those primary sources with added context or information. While both primary and secondary sources are important in scholarship, primary sources are considered the better sources for research as they are the most direct and aren’t filtered by the author of the secondary source.
As such, the best way to cite a secondary source is to not use one. Secondary sources can be valuable for pointing the way to great primary sources, but it’s still best to use the primary source directly.
Still, sometimes it’s not practical to use a primary source. Primary sources may not be in print, may not be translated into a language you can read or simply may not exist anymore. In those cases, it’s important to cite both sources correctly.
That, in turn, can be very difficult. That’s because you can’t just cite the secondary source, you also have to acknowledge the primary source that it’s pulling from.
Generally, this is done through a combination of attribution in the writing itself and works cited. For example, if you want to quote the diary of a historical figure but the diary isn’t available, you could then use a secondary source, such as a biography, to cover it.
In the text of your work, you would say, “In his/her diary, he/she said…” and begin the passage. However, when adding both the in-text citation and the works cited reference, you would refer to the biography, as that is where you got the information.
However, the in-text citation will take a slightly different format. Instead of simply listing the source, you would add “as cited” or “as quoted” to indicate that it is a secondary source. The works cited entry at the end is the same as normal, save in the case of Chicago style where both documents must be cited.
(Note: Since each style has slight differences in the formatting of citations, see this guide for details on formatting secondary source citations in APA, MLA and Chicago.)
When you’re done, it should be clear to the reader that you’re quoting or paraphrasing from the primary source but pulling the information from a secondary source.
That transparency, in the end, is what is important. Hiding either of your sources is a form of plagiarism, so it’s important to be abundantly clear about what you’re quoting/paraphrasing and where you’re pulling that information from.