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 $\SL_2(\ZZ)$, to non-holomorphic quasi-modular forms associated to certain co-compact Riemann-Schwarz triangular subgroups of $\SL_2(\CC)$. 
Federico Pellarin