Supplementary data and suggestions for further reading, maybe

ENDNOTES

Check the back of the book where citations and extra references often gather at the very end.

This clue hints at the extra material you often find at the end of a book or article—things like citations, comments, or references that expand on the main text. "Supplementary data" points to the notes themselves, while "suggestions for further reading" nudges toward the "notes" part of the answer. The word "maybe" signals that "end" isn’t just about location but also part of the answer, combining with "notes" to form "endnotes." It’s a straightforward definition with a slight nudge to think of the term as two parts.