@article{04009334,
title = {Graphs and projective planes in 3-manifolds.},
journal = {International Journal of Mathematics and Mathematical Sciences},
volume = {9},
year = {1986},
pages = {551-560},
doi = {10.1155/S0161171286000698},
zbl = {0622.57007},
language = {en},
url = {http://dml.mathdoc.fr/item/04009334}
}
Heil, Wolfgang; Negami, Seiya. Graphs and projective planes in 3-manifolds.. International Journal of Mathematics and Mathematical Sciences, Tome 9 (1986) pp. 551-560. doi : 10.1155/S0161171286000698. http://gdmltest.u-ga.fr/item/04009334/