Holzschuh Verlag Akkordeon Workshop 1, Method for Accordion, For 48 to 120 basses, By Martina Schumeckers, ISBN 9783920470900, ISMN 9790201301044, publisher's no. VHR 1760, Format: 21 x 30 cm, Spiral binding, 112 Pages, In German, Including audio download and online videos