 by Proposition \[prop-0.0\], a maximal effective prolongation of ${\textswab{m}},$ because ${\mathfrak{g}}$ is simple. Indeed, $${\mathpzc{R}}=\{{\pm}{\mathpzc{e}}_i{\pm}{\mathpzc{e}}_j\mid 0{\leq}i{<}j{\leq}n\}