Similar to front matter, there is material you might wish to include after your book's final <chapter> or your article's final <section>. Possibilities to place in a <backmatter> include <appendix>, <references>, <index-part>, and <colophon>. There are empty tags you can place into an appendix to generate lists of notation, or lists of particular elements of your choice, such as a list of figures. A similar empty element actually generates the index, <index-list />. See Section 6.13 for details on the back matter generally, and Section 6.14 for more on automatic lists.