Fidalgo, P, M P Alves, A Freire, F Batista, A Fernandes, B Gard, F B Barros, and J P Correia. 1989. “ Prevalence and Conditioning Factors”. Acta Médica Portuguesa 2 (2). Lisbon, Portugal:77-82. https://doi.org/10.20344/amp.3461.