## Hypertext Help with LaTeX

### \stackrel

This can be used to stack something above something else; used in math mode.

\stackrel{top}{bot}

The first argument, `top`, is typset immediately above
the second argument, `bot`; the former is set in the same
math style as a superscript.

For example

H$_2$CO$_3$ $\stackrel{\rm heat} {\longrightarrow}$ H$_2$O + CO$_2$

will produce something like

heat H CO ------> H O + CO 2 3 2 2

Note that the the `\rm`
declaration is used so that "heat" is set in Roman face and not
math italics.

### \mathop

This command does not seem to be well documented but appears to work, at least in current versions of LaTeX 2.09.

The argument is considered to be a single variable sized math symbol for purposes of placing limits below (subscripts) and above (superscripts) in display math style. For example,

\mathop{\sum \sum}_{i,j=1}^{N} a_i a_j

would produce something like

N --- --- \ \ / / a a --- --- i j i,j

It is possible to create **two rows** of
"subscripts" by using a similar construction: The first row is
created as subscripts of the symbol in the usual way and a lower
row is created by placing this whole construct as the argument
of a `\mathop` command with its own subscript. For example

\mathop{\sum_{i,j=1}^{N}}_{i>j}

would produce something like

N --- \ / --- i,j=1 i>j

Related topics

- Math Formulas and Math Symbols
- Arrows
- Binary and relational opertors
- Eqnarray Environment
- Equation Environment
- Displaymath Environment
- Math Fonts and Styles

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Revised 15 Aug 1995.