@article{10_4153_CMB_1964_049_x,
     author = {Pullman, N.},
     title = {On the {Number} of {Positive} {Entries} in the {Powers} of a {Non-Negative} {Matrix}},
     journal = {Canadian mathematical bulletin},
     pages = {525--537},
     year = {1964},
     volume = {7},
     number = {4},
     doi = {10.4153/CMB-1964-049-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-1964-049-x/}
}