Anybody in Germany please see what Kathrin Hirzel says about the Prakticello ®.
http://www.kathrinhirzel.de/

Brian Magnus
http://www.brianmagnus.com/

Recordings and Tools for the Developing Musician
http://www.apprenticemusic.com/

Michael Dahlberg
http://www.michaeldahlberg.net/

Cello Joe
http://www.cellojoe.com/

Sheida Davis
http://www.sheidadavis.co.uk/

Cello Professor
http://www.celloprofessor.com/

Miriam Wakeling
https://miriamwakeling.com/