Lemmes de multiplicite associes aux groupes triangulaires de Riemann-Schwarz

In this article, we extend a multiplicity estimate of Nesterenko, valid for quasi-modular forms associated to ${\text{SL}}_2(\text{ZZ})$, to non-holomorphic quasi-modular forms associated to certain co-compact Riemann-Schwarz triangular subgroups of ${\text{SL}}_2(\text{CC})$.