Integral of volume

Question

How i can correct the positioning of the limits of this integral

i would an effect like this...

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\iiint \limits_{-\infty\ -\infty\ -\infty}
    ^{\ \ \ +\infty\ +\infty\ +\infty} 
    \psi_{nlm}(r,\theta,\phi)\, dr\,d\theta\,d\phi

\end{document}

i have found the code below what do you think about it?

\documentclass{article}
\usepackage{amsmath}

\begin{document}
\begin{equation}
\int_{-\infty}^{+\infty}\int_{-\infty}^{+\infty} \int_{-\infty}^{+\infty} \psi_{nlm}(r,\theta,\phi)\, dr\,d\theta\,d\phi=1
\end{equation}
\begin{document}

Answer 1

You could use separate \int\limits... for each one:

\documentclass{article}
\usepackage{amsmath}
\begin{document}

Original:
\[
    \iiint \limits_{-\infty\ -\infty\ -\infty}^{+\infty\ +\infty\ +\infty} \psi_{nlm}(r,\theta,\phi)\, dr\,d\theta\,d\phi=1
\]
Separate:
\[
    \int\limits_{-\infty}^{+\infty} \int\limits_{-\infty}^{+\infty} \int\limits_{-\infty}^{+\infty} \psi_{nlm}(r,\theta,\phi)\, dr\,d\theta\,d\phi=1
\]
\end{document}

In my experience the \iint and \iiint are more useful when you are specifying the region of integration using a local definition- this is what Percusse mentioned in his comment (permission given to post in chat)

\[
    \iiint \limits_{\mathbb{R}\times\mathbb{R}\times\mathbb{R}}\psi_{nlm}(r,\theta,\phi)\, dr\,d\theta\,d\phi=1
\]

On another note, you might like to use \mathrm{d} for the d in each integration.