the SEE ALSO section

In most cases, the SEE ALSO section only contains cross references to other manual pages. Use one Xr macro for each reference, providing the name and the section number of the target page as arguments. Sort the manual page references first numerically by section, then alphabetically by name. Separate the references by commas, putting one comma as a final, third argument after each reference but the last one. Do not put punctuation after the last reference, and do not use display macros or line break macros.
List additional resources, for example web sites or books, after the manual page references. For books, journal articles, technical reports and similar printed documents, use Rs bibliographic blocks, one per document.
For each web site listed, use one Lk macro. Usually each Lk macro only needs one argument, the URI. In some cases, providing a second argument giving a name or description of the website may be useful. In HTML output, that turns into a proper hyperlink, but it may not look good on the terminal with some formatters, so if there is a natural way to use the one argument form, that may be preferable.

The MANUAL STRUCTURE section in the mdoc(7) manual.
September 3, 2015