These stamps have been taken at the CDDR (Centre de documentation pour le dévelopement rural, engl. Documentation Centre for Rural Development) in Yaoundé, Cameroon. The centre has the task to further rural development by providing not only printed resources from its library, but also a hotline for local farmers and the preparation of thematical dossiers.
The stamp looks a little bit crowded, but the writing is only the name and the address of the centre. The number of the book, probably a numerus currens, has been added afterwards by pen.