特殊字元
  空白
""
&&
®®
©©
µ
αα
ββ
γγ
∇
ℜ
µµ
—
→
⇒
↑
&uArr
↓
⇓
←
⇐
↔
⇔
⊕
♠
♥
♦
♣
†
εε
ηη
…
≡
λλ
««
◊

 
數學字元
&lt;<
&gt;>
&le;
&ge;
&ne;
&ang;
&and;
&or;
&pi;π
&sum;
&perp;
&prop;
&plusmn;±
&ni;
&isin;
&notin;
&nsub;
&sub;
&sube;
&supe;
&sup;
&there4;
&there4;&t
&theta;θ
&times;×
&divide;÷
&asymp;
&cap;
&exist;
&empty;
&equiv;
&forall;
&frac12;½
&frac14;¼
&frac34;¾
&infin;
&int;