@article{CMH_1948__21_138949,
     author = {Samuel Eilenberg},
     title = {Relations between cohomology groups in a complex.},
     journal = {Commentarii mathematici Helvetici},
     pages = {302--320},
     publisher = {mathdoc},
     volume = {21},
     year = {1948},
     zbl = {0031.18103},
     url = {http://geodesic.mathdoc.fr/item/CMH_1948__21_138949/}
}