On the Chekhov-Fock coordinates of dessins d'enfants
  There are several ways to associate a complex structure to a ribbon graph. In the construction of dessins d'enfants a single riemann surface is associated to each graph. We call it the Grothendieck model of a ribbon graph. The goal of the present paper is to discuss one more such construction, depending on some parameters - that of Chekhov-Fock. We prove that putting all parametres equal to 0, we obtain the Grothendieck model of this graph. 
G. Shabat, V. Zolotarskaia