Anti-Tumour Activity of Two 19-Nor-clerodane Diterpenes, trans-Dehydrocrotonin and trans-Crotonin, from Croton cajucara - Grynberg, Noema F; Echevarria, Aurea; Lima, Juliana E; Pamplona, Sônia S R; Pinto, Angelo C; Maciel, Maria Aparecida M (Planta Medica, 1999)