I want to know the answer to the following question:
What was the second time period that a significant change began to happen in Cubism?
All the background I'm provided with is that "This grouping of styles of painting and sculpture, especially significant between 1917 and 1920, was practiced by several artists; particularly those under contract with the art dealer and collector Léonce Rosenberg.". Is that enough to answer the question?
Answer: yes