Casseb, J. et al. 2007. T CD4+ cells count among patients co-infected with human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus type 1 (HTLV-1): high prevalence of tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM) . Revista do Instituto de Medicina Tropical de São Paulo. 49, 4 (Aug. 2007), 231–233.