I want to know the answer to the following question:
On which book and who was the author was one of the main sources of the historical study of Cubism based?
All the background I'm provided with is that "It came to rely heavily on Daniel-Henry Kahnweiler's book Der Weg zum Kubismus (published in 1920), which centered on the developments of Picasso, Braque, Léger, and Gris.". Is that enough to answer the question?