Swets & Zeitlinger published in 1968 a book of Gaston Boyer " Un peuple de l'ouest soudanais, les Diawara " which was originally published ( in 1953 ) by the French Institute of Black Africa.

Besides the fact that Gaston Boyer did not seem to have been informed of this new edition to the detriment of copyright, you also assign this book jean Rouch what is wrong.
Contrary to what is stated this book is not Jean Rouch but only Gaston Boyer.
In 1947 as a young student (he was born in 1922) of the colonial administration Gaston Boyer writes his internship thesis on "Un peuple de l'ouest soudanais, les Diawara ".
This memory was noticed by the first director of the Institut français d'Afrique noire ( IFAN) (French Institute of Black Africa) , Théodore Monod (https://fr.wikipedia.org/wiki/Théodore_Monod), who decided to publish Collections IFAN.
In 'Notes Africaines' newsletter and correspondence of the French Institute of Black Africa in January 1953 this book was presented by the writer of the article together with an another book of Jean Rouch "Contribution à l'histoire des Songhai".

Misread the title of the article (which cites 2 different books and authors 2 ) leads to confusion.
Thank you to modify your files , references to this book.