@article{10_4153_CMB_2015_013_3,
     author = {Llamas, Aurora and Mart{\'\i}nez{\textendash}Bernal, Jos\'a},
     title = {Cover {Product} and {Betti} {Polynomial} of {Graphs}},
     journal = {Canadian mathematical bulletin},
     pages = {320--333},
     year = {2015},
     volume = {58},
     number = {2},
     doi = {10.4153/CMB-2015-013-3},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CMB-2015-013-3/}
}