Q. I was wondering: In an academic book is there a reason to put something in a bibliography and not in an endnote? If there is a reason, what is it? What references go in the endnotes then? Is a bibliography needed?
A. A bibliography is optional if the endnotes contain full citations. But some writers use a bibliography to include materials used in researching the document whether they are cited in the notes or not. It can also include suggested readings. For more details, start with CMOS 13.65 and 13.68.