@article{1256053294,
author = {Larmore, Lawrence L.},
title = {The first obstruction to embedding a $1$-complex in a $2$-manifold},
journal = {Illinois J. Math.},
volume = {14},
number = {4},
year = {1970},
pages = { 1-11},
language = {en},
url = {http://dml.mathdoc.fr/item/1256053294}
}
Larmore, Lawrence L. The first obstruction to embedding a $1$-complex in a $2$-manifold. Illinois J. Math., Tome 14 (1970) no. 4, pp. 1-11. http://gdmltest.u-ga.fr/item/1256053294/