Magarão, M. F., et al. “Cellular and Humoral Immunity in Active Pulmonary Tuberculosis. A Study in Patients Reacting to Two Units of PPD”. Revista Do Instituto De Medicina Tropical De São Paulo, vol. 19, no. 1, Feb. 1977, pp. 1-9, https://www.revistas.usp.br/rimtsp/article/view/197763.