A manual for writers of research papers, theses, and dissertations, 7th edition - Kate L. Turabian 2007

Footnotes and parenthetical citations
Parenthetical citations–reference list style: the basic form
Part II. Source Citation

If you wish to make substantive comments on the text, use footnotes instead of parenthetical citations. See 16.3.2—16.3.4 for note placement, numbering, and format. To cite a source within a footnote, use the normal parenthetical citation form.

N: 10. James Wilson has noted that “no politician ever lost votes by denouncing the bureaucracy” (1989, 235).