APA Style (7th ed.)

Many academic books and journal articles quote earlier books or articles on the same topic. If you cannot access the original source, you can cite the secondary source instead. However, you should only cite secondary sources sparingly—for instance, when the original work is out of print, unavailable, or available only in a language that you do not understand.

If possible, find the primary source, read it, and cite it directly rather than citing a secondary source.

Follow these instructions when citing a secondary source:

1. In the reference list, provide an entry for the secondary source that you used.
2. In the text, identify the primary source and write “as cited in” to your in-text citation, along with the details of the source that you are reading.

Boyle's study of childhood obesity (2005, as cited in Smith, 2010) is a landmark in ...

Because you have not viewed Boyle’s work, it only appears in the in-text citation and not in the reference list. The secondary source (Smith, 2010) should be listed in the reference list, according to the normal format for that type of source.