'evident in both their thematic-formal and linguistic aspects'. On the thematicformal aspects, he observes that
interspersing the spoken narrative with sung verses and strophes, with refrains of onomatopoeic effect, is a characteristic, although not exclusive, feature of the African oral tradition. This is a stylistic resource, but its purpose is to support the narrated theme and make the listener feel involved [...] (Pessoa de Castro, 1978, pp. 17, 19).  
João da Silva Campos collected all these tales 'directly from the popular version; and almost all of them in a very restricted area of Bahia's Recôncavo.' He observes that, as far as possible, he 'faithfully reproduced the language of the people, often copying cacophonies, corruptions and solecisms'. This researcher left other scholars with the 'difficult task of classifying' the collection's stories 'by the criterion of origin' (De Magalhães, 1939, p. 177).  
In an appendix, Yeda Pessoa de Castro reproduces seven folk tales from da Silva Campos' collection, the origins of which she identifies as one Yoruba and six Bantu, from the Kibungo cycle. From this same cycle, she also reproduces a folk tale collected by Basílio de Magalhães and two collected by Nina Rodrigues in Salvador, three collected by Souza Carneiro in the Recôncavo and in Salvador, and one from Lindolfo Gomes' collection from Minas Gerais. Through this comparative work, the researcher clearly brings out the strong contribution of the Bantu oral tradition to the formation of the Brazilian oral tradition.