@article{article10e015fa,
title   = {`sigma´- and `pi´- defects at graphene nanoribbon edges: building spin filters},
author = {Martins, Thiago Barros and Silva, Antonio Jose Roque da and Miwa, Roberto Hiroki and Fazzio, Adalberto},
year = {2008},
journal   = {Nano Letters}
}