Lateritic weathering effects over phosphatic Brazilian ores: Catalão I and Juquia (Brasil) - Toledo, Maria Cristina Motta de; Ferrari, Viviane Carillo; Santos, C. N.; Alcover Neto, Arnaldo; Perseval, Ph. de; Fontan, F; Ribeiro, C. C (International Geochemical Exploration Symposium, 1999)