<p>I think you have to use <code>unicode</code> within the $\LaTeX$ code:</p>

<blockquote>
  <p><code>$ {\bf \unicode[Times]{x3B1}} $</code></p>
  
  <p><code>$ {\bf \unicode[Times]{x3B2}} $</code></p>
  
  <p><code>$ {\bf \unicode[Times]{x3B3}} $</code></p>
</blockquote>

<p>will result in </p>

<blockquote>
  <p>$ {\bf \unicode[Times]{x3B1}} $</p>
  
  <p>$ {\bf \unicode[Times]{x3B2}} $</p>
  
  <p>$ {\bf \unicode[Times]{x3B3}} $</p>
</blockquote>

<p>See the <a href="http://en.wikipedia.org/wiki/Greek_alphabet#Greek_in_Unicode" rel="nofollow">Wikipedia page</a> for the Greek Alphabet for the unicode for each letter.</p>

<p>Note that you can use regular $\LaTeX$ commands for upright uppercase Greek letters with <code>\rm</code>. For example, using:</p>

<blockquote>
  <p><code>$ {\rm A, B, \Gamma} $</code></p>
</blockquote>

<p>results in </p>

<blockquote>
  <p>$ {\rm A, B, \Gamma} $</p>
</blockquote>
