Marçal Júnior, Oswaldo, et al. “ Schistosomiasis Mansoni in an Area of Low Transmission: II. Risk Factors for Infection ”. Revista Do Instituto De Medicina Tropical De São Paulo, vol. 35, no. 4, Aug. 1993, pp. 331-5, https://www.revistas.usp.br/rimtsp/article/view/29054.