Actually Rogers Fry's Vision and Design [1920] was the most lucky discovery for me. I came on it by chance while looking for another book in the Leeds Reference Library. Fry in his essay on 'Negro Sculpture' stressed the 'three-dimensional realization' that characterized African art and its 'truth to material'. More, Fry opened the way to other books and to the realization of the British museum. That was really the beginning.