!-- tilde operator is NOT the same character as the tilde, U+007E,
     although the same glyph might be used to represent both  --&gt;
&lt;!ENTITY cong     CDATA "&amp;#8773;" -- approximately equal to, U+2245 ISOtech --&gt;
&lt;!ENTITY asymp    CDATA "&amp;#8776;" -- almost equal to = asymptotic to,
                                     U+2248 ISOamsr --&gt;
&lt;!ENTITY ne       CDATA "&amp;#8800;" -- not equal to, U+2260 ISOtech --&gt;
&lt;!ENTITY equiv    CDATA "&amp;#8801;" -- identical to, U+2261 ISOte