@article{10_4153_CMB_1988_021_x,
     author = {Bastos, Gervasio G. and Viswanathan, T. M.},
     title = {Torsion-free {Abelian} {Groups,} {Valuations} and {Twisted} {Group} {Rings}},
     journal = {Canadian mathematical bulletin},
     pages = {139--146},
     year = {1988},
     volume = {31},
     number = {2},
     doi = {10.4153/CMB-1988-021-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1988-021-x/}
}