USARet Major James Gebhardt translated the "Official" Soviet Mosin Sniper Rifle Manual.
Here is a link:
http://www.amazon.com/Official-Soviet-Mosin-Nagant-Sniper-Manual/dp/1581607369
This is a Palladin book, so you can find info elsewhere. There are clear, concise descriptions for how to quickly and precisely find the center (COI) of a group, along with instruction on use of the PU (and other) optical sights. Interesting stuff!