# How come Revtex says acknowledgements are obsolete?

Running revtex4-1 with the preamble:

\documentclass[aps, pre, floatfix, reprint]{revtex4-1}


and the section later:

\begin{acknowledgements}
The authors would like to thank Tex, LaTeX and Friends
for the answer to this question.
\end{acknowledgements}


Gives the warning:

 Class revtex4-1 Warning: Environment acknowledgements is obsolete;


Have I done something wrong here?

-
If I could (rep. deficient) I would tag this as 'revtex' but no tags exists at the moment. – Hooked Aug 16 '10 at 17:30
Tagged it for you. – Caramdir Aug 16 '10 at 17:32
Very nice example! Since it's not an error, I changed that tag to [warning]. – Stefan Kottwitz Aug 16 '10 at 17:51

I have never used revtex but the author's guide explicitly states:
So replacing acknowledgements by acknowledgments removes the message.