bf­symb – Gen­er­ate bold sym­bols in Plain TeX math­e­mat­ics

De­fines a com­mand \boldsym­bol that rep­re­sents its ar­gu­ment us­ing the cm­mib10 rather than the font cur­rently in use. This tech­nique has its lim­i­ta­tions (the com­mand of the same name in the AMS-LaTeX bun­dle is much clev­erer), but a sim­ple \boldsym­bol{\beta} does the job ex­actly.