Why does dgroup not create equation numbers?

Question

I have a tex file:

\documentclass{minimal}
\usepackage{breqn}
\begin{document}
 \begin{dgroup}
  \begin{dmath*}
   0 = x + y
  \end{dmath*}
  \begin{dmath*}
   3 = 2x + 4y
  \end{dmath*}
 \end{dgroup}
\end{document}

I think, that pdflatex should produce two lines of equations with one common number on the right. But I do not get this number. In http://www.tug.org/TUGboat/tb18-3/tb56down.pdf on page 9/10 there is some example about that (the example code is from there). The official doc of breqn does not say it clearly, but I think it should work.

Can you tell me what's going wrong here? How to get the equation number correctly?

Besides: Are there "better packages" than breqn? I am used to use it as it breaks equations automatically which is very useful in case of narrow pages.

Answer 1

I think it should be:

\documentclass{minimal}
\usepackage{breqn}
\begin{document}
 \begin{dgroup*}
  \begin{dmath}
   0 = x + y
  \end{dmath}
  \begin{dmath}
   3 = 2x + 4y
  \end{dmath}
 \end{dgroup*}
\end{document}

\begin{dmath*} creates an equation without number...

\begin{dgroup} will introduce another numbering (subnumbering)