Re: [Groff] bold greek, e.g. sigma ?

[Tadziu Hoffmann]

> Is it possible to have bold greek letters?

With groff as distributed, using the Postscript device,
it's not possible.  You will need to install either a bold
text font that contains Greek letters or a bold symbol font
(plus a corresponding non-bold symbol font for consistency).
For the latter you can use TeX's Computer Modern fonts, the
fonts distributed with Mathematica, the STIX project fonts
or those from its precursor ESSTIX, or probably a number of
other fonts available on the Web.
(Depending on how the characters in the font are named
you may need to create a custom map file for afmtodit
and encoding file for grops.)