Brown, R. (1989), “Triadic Van Kampen theorems and Hurewicz theorems”, Contemporary Mathematics, 96: 39–57, ISSN0040-9383
Brown, Ronald; Higgins, P. J. (1981), “Colimit theorems for relative homotopy groups”, Journal of Pure and Applied Algebra, 22: 11–41, doi:10.1016/0022-4049(81)90080-3, ISSN0022-4049
Brown, R.; Loday, J.-L. (1987), “Homotopical excision, and Hurewicz theorems, for n-cubes of spaces”, Proceedings of the London Mathematical Society. Third Series, 54: 176–192, doi:10.1112/plms/s3-54.1.176, ISSN0024-6115