I would like to know what is the latex command to include a double lower index using sigma notation (i.e: second index lies underneath the first index)?

I tried typing:

```
\displaystyle\sum_{m,n=-\infty, \; (m,n)\neq (0,0)}^{\infty}
\left[
\frac{1}{(z-2 m\omega_{1} - 2 n\omega_{2})^{2}}
-\frac{1}{ 4(m\omega_{1} + n\omega_{2})^{2}}
\right]
```

I would appreciate the assistance. Thanks

## Best Answer

The

`\substack`

command from the`amsmath`

package can do what you are after:Or without the comma, since the next condition is on a new line: