Proof of Equation (2.12)
\begin{equation*}
\Gamma \left( -r+1 \right)=-r\Gamma \left( -r \right)
\end{equation*}
Proof:
\begin{align*}
\Gamma \left( -r+1 \right) &={{c}^{-r+1}}\exp (-c)h_{-r}^{-c}{{|}_{c\to \infty }} \\
& ={{c}^{-r+1}}\exp (-c)\left\{ -{{c}^{-1}}-r{{c}^{r-1}}\exp (c)\Gamma \left( -r \right) \right\}{{|}_{c\to \infty }} \\
& =-{{c}^{-r}}\exp (-c)-r\Gamma \left( -r \right){{|}_{c\to \infty }} \\
& =-r\Gamma \left( -r \right) \\
\end{align*}
$\square$