Helbling Verlag Soundbellows Grundlagen, Introduction to Playing with Soundbellows, *This book is written in the German language*, By Gert Balzer and Axel Eickhoff, For varied use in the classroom, ISBN 9783862274239, Catalogue Nr. S8942, Format: DIN A4, 76 pages, Includes CDs with demo and play-along recordings (additionally available streaming via app)