@article{10_4153_CJM_1978_001_x,
     author = {Alex, Leo J. and Morrow, Dean C.},
     title = {Index {Four} {Simple} {Groups}},
     journal = {Canadian journal of mathematics},
     pages = {1--21},
     year = {1978},
     volume = {30},
     number = {1},
     doi = {10.4153/CJM-1978-001-x},
     url = {http://geodesic.mathdoc.fr/articles/10.4153/CJM-1978-001-x/}
}