 indecomposable objects and irreducible morphisms $$\begin{diagram}[labelstyle=\scriptstyle,width=0ex]     M_q & \rTo^{\mu_q} & M_{q-0} & \rTo^{\mu_{q-0}}     & \cdots & \rTo^{\mu_0} & M_0 \\   \end{diagram}$$ in $\DcR$ with $\mu_0 \circ \cdots \circ \mu_q \not= 0$. 