@article{10_4064_sm179_1_7,
     author = {Nobuaki Obata},
     title = {Positive $Q$-matrices of graphs},
     journal = {Studia Mathematica},
     pages = {81--97},
     publisher = {mathdoc},
     volume = {179},
     number = {1},
     year = {2007},
     doi = {10.4064/sm179-1-7},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/sm179-1-7/}
}