Numbers in parentheses refer to specific chapters and sections in The Chicago Manual (18th ed.)
Sometimes an author will quote work someone else has done, but you are unable to track down the original source. In this case, both the original and the secondary source must be listed in the note and the bibliography.
If, for example, you were reading the book The Birth of Feminism: Women as Intellect in Renaissance Italy and England and the author, Sarah Gwyneth Ross, made reference to the article "The Educational Ideas of Christine de Pisan," by Astrik L. Gabriel, but you could not find a copy of Gabriel's article you would refer to it as per the layout below.
1. Author First Name Surname {original author}, Title (Year): page number, quoted in Author First Name Surname {the author of the book that refers to the thoughts/ideas of the other author}), Title (Publisher, Year), page #.
2. Author Surname {original author}, Title, page #.
Author Surname, First Name {original author}. Title. Publisher, Year. Quoted in Author First Name Surname {the author of the book that refers to the thoughts/ideas of the thoughts/ideas of the other author}. Title. Publisher, Year, page #.
1. Astrik L. Gabriel, "The Educational Ideas of Christine de Pisan," Journal of the History of Ideas 16, no. 1 (1995): 3-21, quoted in Sarah Gwyneth Ross, The Birth of Feminism: Women as Intellect in Renaissance Italy and England (Harvard University Press, 2009), 23.
2. Gabriel, "The Educational Ideas," 3-21.
Gabriel, Astrik L. "The Educational Ideas of Christine de Pisan." Culture and Imperialism: Journal of the History of Ideas 16, no. 1 (1995). Quoted in Sarah Gwyneth Ross. The Birth of Feminism: Women as Intellect in Renaissance Italy and England. Harvard University Press, 2009, 23.