Part III describes the Unix tools for document formatting. These tools are no longer part of standard SVR4 but are provided in the BSD compatibility packages that come with SVR4. They do come as a standard part of Solaris (with the exception of pic).
Many Unix vendors supply an enhanced set of formatting tools -- in some cases, as an extra cost option.
Chapter 12: nroff and troff
Chapter 13: mm Macros
Chapter 14: ms Macros
Chapter 15: me Macros
Chapter 16: man Macros
Chapter 17: troff Preprocessors