- E-bookThe First Studies for Every Piano Student as the Technical Foundation for VirtuosityLouis Köhler
- E-bookKöhler - The Easiest Exercise Pieces for piano Op.190Louis Köhler
- E-bookKöhler - Little School of Piano Velocity Op.242Louis Köhler
- E-bookKöhler - New School of Velocity for Piano Op.128Louis Köhler