Let $n = pq$ be a Blum integer, where $p$ and $q$ are prime numbers, and $y$ belongs to the Quadratic Residues modulo $n$ ($y \in QR(n)$).
How could I prove that the primitive square root $x$ of $y$ is given by the following formula? $$ x = y^{\frac{(p-1)(q-1)+4}{8}} mod(n)$$
This question is based on the inverse function of page 31 of this set of notes.