  The Jacobi--Trudi identity associates a symmetric function to any integer
sequence. Let $\Gamma_{(t|X)}$ be the vertex operator defined by
$\Gamma_{(t|X)} s_\alpha =\sum_{n \in \mathbb{Z}} s_{(n,\alpha)} [X] t^n$. We
provide a combinatorial proof for the identity $\Gamma_{(t|X)} s_\alpha =
\sigma[tX] s_{\alpha}\big[x-1/t\big] $ due to Thibon et al. We include an
overview of all the combinatorial ideas behind this beautiful identity,
including a combinatorial description for the expansion of $s_{(n,\alpha)} [X]
$ in the Schur basis, for any integer value of $n$.
