Question

If they are both written by the same author, do I cite a preface to a book as a separate entry from the book itself?

Answer 1

I'm not sure if you have too, but it's always better to do extra citations than not enough citations. So I would recommend citing it in a separate entry. Additionally, a preface is a different work than the book itself. Different editions may have different prefaces, so I would doubly suggest citing it as a different entry.

Answer 2

I agree with his (^) comment: "it's always better to do extra citations than not enough citations." However, if the preface of the book is written by the author, you only have to cite the book once. Because different editions of the same book are typically published on different dates, the citation does not need to be separate. If you are citing correctly, the full citation will include the publishing date. I suggest citing it once, as long as it is done correctly.