Z + in latex code example

Example: Z language latex

\usepackage{oz, amsfonts}

\begin{schema}{MusicStore}
member: \pset NAME\\
orders: \pset (NAME\times ALBUM)\\
owns: \pset (NAME\times ALBUM)
\ST
{\bf dom}\mbox{ } orders \subseteq member\\
{\bf dom}\mbox{ } owns \subseteq member\\
\forall (m, a)\in orders.(m, a)\notin owns
\end{schema}