Genetic alterations in Ki-ras and Ha-ras genes in juvenile nasopharyngeal angiofibromas and head and neck cancer - Coutinho, Claudia Malheiros; Bassini, Alessandra Simoes; Gutierrez, Leonardo Guilhermino; Butugan, Ossamu; Kowalski, Luiz Paulo; Brentani, Maria Mitzi; Nagai, Maria Aparecida (São Paulo Medical Journal=Revista Paulista de Medicina, 1999)