\[{{}_{2}\phi_{1}}\left({a,b\atop c};q,z\right)=\left(\frac{-1}{2\pi i}\right)%
\frac{\left(a,b;q\right)_{\infty}}{\left(q,c;q\right)_{\infty}}\int_{-i\infty}%
^{i\infty}\frac{\left(q^{1+\zeta},cq^{\zeta};q\right)_{\infty}}{\left(aq^{%
\zeta},bq^{\zeta};q\right)_{\infty}}\frac{\pi(-z)^{\zeta}}{\sin\left(\pi\zeta%
\right)}\,\mathrm{d}\zeta,\]