The Heirloom Documentation Tools provide troff, nroff, and related utilities to format manual pages and other documents for output on terminals and printers. They are portable and enhanced versions of the utilities released by Sun as part of OpenSolaris, and, for pic, grap, mpm, and some minor parts, by Lucent as part of Plan 9. WWW: http://n-t-roff.github.io/heirloom/doctools.html