# Why does amsmath print a warning about a foreign command?

I was wondering what was the cause of the following warning message with the specific \usepackage used below:

Using the following:

### Preamble

\documentclass[amssymb,twocolumn,aps]{revtex4}
\usepackage{times,amsmath,latexsym}

### Warning message

Package amsmath Warning: Foreign command \atopwithdelims;
(amsmath)                \frac or \genfrac should be used instead
(amsmath)                 on input line 56.

Line 56

$\frac{gcd(m,n)}{n} {n\choose m}$ is an integer for all pairs of integers $n\geq m\geq 1$.

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What is on line 56 of your file? –  Matthew Leingang Jun 1 '11 at 10:48
@Matthew Leingang: It's classified top secret info, I wouldn't be able to disclose that with you, I am sorry. Just joking, it was cool pretending to be a agent there for a bit. It is here below: $\frac{gcd(m,n)}{n} {n\choose m}$ is an integer for all pairs of integers $n\geq m\geq 1$. –  night owl Jun 1 '11 at 12:16
Aha. Replacing n \choose m with \binom{n}{m} will make the warning go away. –  Matthew Leingang Jun 1 '11 at 14:30
@Matt: Thank You, that sure did take care of it flawlessly. –  night owl Jun 1 '11 at 15:49