Scientific treatises

Sakharov wants you to find and bring him four workbooks from the secret labs throughout the Zone, written by the scientists who continued to work in the labs after the second Blowout. He promises a Pellicle recipe for that.
== Walkthrough ==
Exact location of the treatises is shown on the video:
The fourth one is located in the Warlab, which is unlocked much later than others - in Territory exploration, after completing the Search for the mysterious stalker storyline.
After you obtained all four treatises, report to Sakharov. He will thank you and direct to Wolf who has a gift for you.
== Notes ==
* Completing this quest splits the game plot into two huge parts.
** Talking to Wolf for your reward promised by Sakharov (OP branch) will eventually open Eastern Pripyat, Zaton, Jupiter, and other locations to the east, as well as the Sniper and other major questlines, and also upgrade the Monolith enemies to become tanky, essentially making smaller calibers obsolete.
** Continuing with the Warlab quests (NS branch) will eventually open Red Forest, Limansk, Old Village, Generators, and other locations to the west. You can do either both simultaneously or choose the one you like, but you'll have better rewards if you follow the "OP branch" at least initially.
== Bugs ==