Variations in E, Sonata in C Minor (Op. 4), Rondo in C (version for 1 piano). PWM's National Edition is an ongoing research project, gathering together all available source materials and producing definitive publications. Under the direction of Jan Ekier, his team uses the latest techniques to assess the composerÂ's intentions and relates this to modern pianos and performance. Each volume includes an abridged source commentary and performance commentary, along with snippets of relevant correspondence about the pieces.