Conway, John Horton, A perfect group of order 8,315,553,613,086,720,000 and the sporadic simple groups, Proceedings of the National Academy of Sciences of the United States of America, 1968, 61 (2): 398–400, MR 0237634, doi:10.1073/pnas.61.2.398
Conway, John Horton, A group of order 8,315,553,613,086,720,000, The Bulletin of the London Mathematical Society, 1969, 1: 79–88, ISSN 0024-6093, MR 0248216
doi.org
Conway, John Horton, A perfect group of order 8,315,553,613,086,720,000 and the sporadic simple groups, Proceedings of the National Academy of Sciences of the United States of America, 1968, 61 (2): 398–400, MR 0237634, doi:10.1073/pnas.61.2.398
worldcat.org
Conway, John Horton, A group of order 8,315,553,613,086,720,000, The Bulletin of the London Mathematical Society, 1969, 1: 79–88, ISSN 0024-6093, MR 0248216