\newcommand{\N}{\mathbb N}
\newcommand{\Q}{\mathbb Q}
\newcommand{\R}{\mathbb R}
\newcommand{\Z}{\mathbb Z}

\newcommand{\morph}{\mathop{\longrightarrow}\limits}
\newcommand{\coker}{\operatorname{coker}}

\newcommand{\ds}{\displaystyle}
\newcommand{\sss}{\scriptscriptstyle}
