Let $\lambda,\mu,\nu$ be some partitions. Let's denote with $s_\lambda,s_\mu,s_\nu$ the Schur functions associated to these partitions. If
$s_\mu s_\nu=\sum_\lambda c^\lambda_{\mu\nu}s_\lambda$
then the Schur skew function is
$s_{\lambda/\mu}=\sum_\nu c^\lambda_{\mu\nu}s_\nu$
how can I prove that $s_{\lambda/\mu}=\sum_T x^T$ where $T$ is a tableaux of shape $\lambda/\mu$? (so we are supposing that $\mu\subset\lambda$)
(I know that $c^\lambda_{\mu\nu}=0$ if $|\lambda|\neq |\mu|+|\nu|$)