Apologies for delay, (perhaps you've found your info elsewhere now) but there is a good list of sources in this earlier answer by u/Rhodis

If you are also interested in Lithuania, have a look at S.C. Rowell, Lithuania Ascending: A Pagan Empire within East Central Europe 1295-1345 (1994) and
Darius Baronas & S.C. Rowell, The Conversion of Lithuania: From Pagan Barbarians to Late Medieval Christians (2015)