@article{JRAM_1981__321_152313,
     author = {Johannes Huebschmann},
     title = {Group extensions, crossed pairs and an eight term exact sequence.},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {150--172},
     year = {1981},
     volume = {321},
     zbl = {0441.20033},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1981__321_152313/}
}