Add clarification around lower-greek style usage

Relates to #17 and w3c/csswg-drafts#135

index.html

@@ -884,7 +884,7 @@ <h2>Greek</h2>
 }
 </bdo></code></div>
 
-<p class="note">The <code class="kw" translate="no">lower-greek</code> style is  defined in the <a href="https://www.w3.org/TR/css-counter-styles-3/">CSS Counter Styles Level 3</a> specification, however the <code class="kw" translate="no">greek-lower-modern</code> style is more commonly used in Greece. CSS2.1 included the <code class="kw" translate="no">lower-greek</code> keyword, and at the time of writing, all major browsers support the <code class="kw" translate="no">lower-greek</code> counter style but not the <code class="kw" translate="no">greek-lower-modern</code> style.</p>
+<p class="note">The <code class="kw" translate="no">lower-greek</code> style is  defined in the <a href="https://www.w3.org/TR/css-counter-styles-3/">CSS Counter Styles Level 3</a> specification, however the <code class="kw" translate="no">greek-lower-modern</code> style is more commonly used in Greece. CSS2.1 included the <code class="kw" translate="no">lower-greek</code> keyword, which <a href="https://github.com/w3c/csswg-drafts/issues/135#issuecomment-248303975">it appears</a> is used in mathematical texts, rather than ordinary Greek text. At the time of writing, all major browsers support the <code class="kw" translate="no">lower-greek</code> counter style but not the <code class="kw" translate="no">greek-lower-modern</code> style.</p>
 </section>