Thanks for the tip. Only I didn't find the info I needed in the suggested link. On the other hand I found this discussion which is the answer of my problem:
https://www.mobileread.com/forums/sho...d.php?t=114745
I downloaded the version of poterm for the new API from:
https://www.mobileread.com/forums/att...6&d=1296078465
This version runs fine on my PocketBook 903. Thanks again for the quick reply.