Different methods to write Bold symbols
http://mirror.kumi.systems/ctan/info/symbols/comprehensive/symbols-a4.pdf
Scott Pakin &lt;scott+clsl@pakin.org&gt; ∗;

∗ The original version of this document was written by David Carlisle, with several additional tables provided by Alexander Holt. See Section 10.8 on page 230 for more information about who did what.