@article{articled8cbf356,
title   = {Diagonal approximation and the cohomology ring of the fundamental groups of surfaces},
author = {Gonçalves, Daciberg Lima and Martins, Sérgio Tadao},
year = {2015},
doi = {10.1007/s40879-014-0031-3},
journal   = {European Journal of Mathematics}
}