@article{10_4064_cm122_2_2,
     author = {Nobuaki Obata},
     title = {Markov product of positive definite kernels and applications to $Q$-matrices of graph products},
     journal = {Colloquium Mathematicum},
     pages = {177--184},
     publisher = {mathdoc},
     volume = {122},
     number = {2},
     year = {2011},
     doi = {10.4064/cm122-2-2},
     language = {en},
     url = {http://geodesic.mathdoc.fr/articles/10.4064/cm122-2-2/}
}