# 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.

# Hypertext Help with LaTeX
a name="mathop">\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

- `\overbrace`
- `\overline`
- `\underbrace`
- `\underline`

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