Christer Bergström, known for many WWII aviation books, has announced recently that long awaited Volume 4 of Black Cross/Red Star has been printed recently.
New book is apparently larger then earlier ones in this series. See it compared to the Volume 2.
I just would like to emphasize that the author was one of the most respected contemporary Russian aviation historians, all his books contain many important details. To the greatest regret, Vladimir Kotelnikov passed away two years ago.