3-regular colored graphs and classification of surfaces
  Motivated by the theory of crystallizations, we consider an equivalence relation on the class of $3$-regular colored graphs and prove that up to this equivalence (a) there exists a unique contracted 3-regular colored graph if the number of vertices is $4m$ and (b) there are exactly two such graphs if the number of vertices is $4m+2$ for each $m\geq 1$. Using this, we present a simple proof of the classification of closed surfaces. 
Biplab Basak
math.CO