Petrological and geochemical studies of alkaline rocks from continental Brazil. 6. The phonolite-tephrite suite from Fortaleza, State of Ceará - Beccaluva, Luigi; Almeida, Afonso Rodrigues de; Barbieri, Mario; Brotzu, Pietro; Coltorti, Massimo; Conte, Aida; Garbarino, Carlo; Gomes, Celso B.; Macciotta, Giampaolo; Morbidelli, Lucio; Ruberti, Excelso; Traversa, Gianbosco (International Conference, 1988)