@article{10_21136_MB_2007_134191,
     author = {Okamoto, Futaba and Zhang, Ping and Saenpholphat, Varaporn},
     title = {On $\gamma $-labelings of oriented graphs},
     journal = {Mathematica Bohemica},
     pages = {185--203},
     publisher = {mathdoc},
     volume = {132},
     number = {2},
     year = {2007},
     doi = {10.21136/MB.2007.134191},
     mrnumber = {2338805},
     zbl = {1174.05056},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.21136/MB.2007.134191/}
}