Hi well i'm preparing to enter to the conservatory, and i started to practice more than i used to, i want to start to practice 13 hours a day, but i need good excercises, you know, i'm thinking about czerny, right now, i need excercises to improve the agility of my left hand, i also need excercises for trills, especially with the LH, i'm working with the school of velocity of czerny, i saw czerny's "school for the left hand", but i think i need to start from something more basic, could you recommend me a book? i already have "the virtuoso panist" but i need to concentrate on my left hand, Thanks!