For instance, the author that is commentating on the primary source is named Foster.
The primary source is Dante's Inferno. I want to make reference to the primary source that Foster is addressing in the in-text citation but I also want to reference Foster.
In APA format, should the sentence look like this:
Foster (1964) notes that Dante makes use of x, y and z (p. 101, Inf. XVI, 23).
p. 101 is for Foster, while Inf. XVI, 23 is for Dante.
What you have is not clear: it looks like “p. 101” refers to Dante’s Inferno. Instead, I would put the page number for Foster with the year for that source, not at the end, if you even include it at all (not being a direct quote, it is not required). In APA, you don’t need to put the page number at the end of the sentence:
“A flexible mind is a healthy mind,” according to Palladino and Wade’s (2010, p. 147) longitudinal study.
Because you mention the sources separately by name, you should have completely separate parentheticals. Compare the examples for multiple in-text citations.
If you cite Foster verbatim, you give his citations as they appear in his text:
"Dante (Inf. XVI, 23) makes use of x, y, and z." (Foster, 1964, p. 101)
If you refer to Foster indirectly, paraphrase the citation:
Foster (1964, p. 101) notes that Dante makes use of x, y, and z in canto XVI, verse 23, of Inferno.
Since you will probably use Foster's argument in a context where you are already talking about Inferno or that passage in particular, you may skip part of the reference to Dante's work:
While Dante has avoided [whatever x, y, and z are] throughout most of canto XVI, Foster (1964, p. 101) noted that he makes use of x, y, and z when Vergil encounters Rusticucci, Guerra, and Aldobrandi at the waterfall.
