Use documentation for the Mathematical Markup Language (MathML) Tag Set (http://www.w3.org/TR/MathML2/) or for the Mathematical Markup Language (MathML) 3.0 Tag Set (http://www.w3.org/TR/MathML3/).
| Value | Meaning |
|---|---|
| An identifier (IDREF) | Points to another MathML element. Use MathML documentation. |
| Restriction: | |