Used Accordion Etude Book - The Art of Muscular and Finger Control for the Piano Accordion by Frank Gaviani
"The principal difficulty in piano accordion playing does not consist in the reading of music but in the weakness of the fingers. In the opinion of many, the chief difficulty to be overcome in studying an instrument consists in learning to read music. But this is by no means the case. The reading of music is learned in the same manner as a child learns to read letters. The first difficulties having been mastered, the task is easy; as with a printed book, so with music."