Steam Community :: Guide :: Right behind you. A guide to Spy.
The Invisible Library (The Invisible Library Novel): Cogman
Steam Community :: Guide :: TF2 Guide - Beginner Spy
Steam Community :: Guide :: Big Bad Balisong - A guide to Spy Knives
Team Fortress 2 - Wikipedia
Karambit Knife, Resident Evil Wiki
Steam Community :: Guide :: The Black Rose
Steam Workshop::Enhanced Spy Items
Steam Community :: Guide :: TF2 Spy Knives Guide
Steam Community :: Guide :: MVM Spy Guide
Item drop system - Official TF2 Wiki