Question: What portion of the reconstruction of Saint Denis was begun after the completion of the west front?
Sentence: To achieve his aims, his masons drew on the several new features which evolved or had been introduced to Romanesque architecture, the pointed arch, the ribbed vault, the ambulatory with radiating chapels, the clustered columns supporting ribs springing in different directions and the flying buttresses which enabled the insertion of large clerestory windows.
Answer in sentence: no