This is my solution:
\usepackage{enumitem}
\renewcommand{\labelenumi}{\textbf{Specification \arabic{enumi}: }}
\begin{enumerate}[leftmargin=0cm,itemindent=.5cm,labelwidth=\itemindent,labelsep=0cm,align=left]
\item XY mus hold
Some explanation
\begin{equation}
A = B + C
\end{equation}
%% Next item ...
\end{enumerate}
Because I splitted the items into several files I use resume to continue my enumeration:
\begin{enumerate}[resume, leftmargin=0cm,itemindent=.5cm,labelwidth=\itemindent,labelsep=0cm,align=left]
\end{enumerate}
With this I can reference formulas and equations everywhere in my document.
subsectionorsubsubsectionorparagraph– Marco Daniel Jun 18 '12 at 19:16