"Secondary Sources" or "Indirect Sources" (Sec. 14.260)
If you choose to quote work that is used in the resource you are using, you are encouraged to find the original work. There are cases where you might be 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. Cite the original and secondary source based on their publication type (i.e., book/article), linked with the "quoted in" information.
If you were reading a book and the author of the book (in the example below, that would be A. Cairns) made reference to the work done by another author (in the example below, that would be Edward A. Said), you would refer to the work using the format listed below:
Original Author: author of the original source
Secondary Source Author: the author of the book/article that refers to the thoughts/ideas of the original author