The National Defence University´s Library answered to your question and gave a list of references below. Most of the source books on the subject are available only in Finnish. However, in Kari Kuusela´s book there is a short chapter in English about German Assault Gun Brigade seconded to the Finnish Army during the Battle of Tali-Ihantala. I hope you find these books useful! Käkelä, Erkki. Laguksen rynnäkkötykit : rynnäkkötykkipataljoona 1943-1944 / Erkki Käkelä. Porvoo ; WSOY, 1996. ISBN...24.8.2010 12:50Helsingin kaupunginkirjasto