\[U'\left(-\tfrac{1}{2}\mu^{2},\mu t\sqrt{2}\right)\sim-\frac{\mu}{\sqrt{2}}g(%
\mu)(t^{2}-1)^{\frac{1}{4}}\*e^{-\mu^{2}\xi}\sum_{s=0}^{\infty}\frac{{\cal B}_%
{s}(t)}{\mu^{2s}},\]