APA (7th ed.) Citation Style Guide: Secondary Sources

Secondary sources are also sometimes called "indirect citations."

As per the Publication manual of the American Psychological Association (2020):

• In scholarly work, a primary source reports original content; a secondary source refers to content first reported in another source.
• 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, as a matter of good scholarly practice, find the primary source, read it, and cite it directly rather than citing a secondary source. For example, rather than citing an instructor's lecture or a textbook or encyclopedia that in turn cites original research, find, read, and cite the original research directly (unless an instructor has directed you to do otherwise).
• When citing a secondary source, provide a reference list entry for the secondary source that you used. In the text, identify the primary source and then write "as cited in" the secondary source that you used.
• For example, if you read a work by Lyon et al. (2014) in which Rabbitt (1982) was cited, and you were unable to read Rabbitt's work yourself, cite Rabbitt's work as the original source, followed by Lyon et al.'s work as the secondary source.

(Rabbitt, 1982, as cited in Lyon et al., 2014)

Only Lyon et al.'s work appears in the reference list.

An example of a secondary source citation can be found below and another example is on p.5 of the Sample Annotated Student Paper from APA.   In the annotated student paper example the year of the primary source is known so it is included.  If the year of the primary publication is known, include it in-text; if the year of the primary sources is not known, it can be omitted from the in-text citation. 

In Text examples

In Warkinton’s study (as cited in Roberts, 2020), children’s cognitive growth and development …

Or

Roberts (2020) examined Warkinton’s study on children’s cognitive growth and development……

Reference List examples

Roberts, M. (2020). Children and cognition and the development of language. Psychological Reports, 19(7), 412-419.

Note: You only include resources you accessed/read in your References list - you read the Roberts article (which referenced the Warkington article) so the Roberts article is included in your list of References (not the Warkington article).