1. Department of Earth Sciences, Geosciences Centre, University of Coimbra, Rua Sílvio Lima, 3030-790 Coimbra, Portugal
2. Higher Institute of Education and Communication, University of São Tomé and Príncipe, Rua da Caixa, nº19-C.P. 546, São Tomé, São Tomé and Príncipe, 3030-790 Coimbra, Portugal