If you like to find more exercises about the Thumb Positions (Cr.-S.cr - Diat.) following Petracchi's School, you might give a look at these new exercises which I have added in the section "Technique for double bass" and written by maestro MICHELE CELLARO.
BTW., in all the site you can find something interesting ... I hope!
"We all must thank you, Dear Vito, for your tireless work for all of us bassists!" You are doing so much for your colleagues and your art.
PIERMARIO MURELLI - "Nuova didattica per contrabbasso " Ed. RICORDI