@article{MAN_1923__90_159017,
     author = {H. K\"unneth},
     title = {\"Uber die {Bettischen} {Zahlen} einer {Produktmannigfaltigkeit.}},
     journal = {Mathematische Annalen},
     pages = {65--85},
     publisher = {mathdoc},
     volume = {90},
     year = {1923},
     zbl = {49.0408.01},
     url = {http://geodesic.mathdoc.fr/item/MAN_1923__90_159017/}
}