Where is the last arkham chronicle located in the game batman: arkham asylum?

so... I've completed every riddler challenge but i still didn't find all the arkham chronicles. Am i supposed to find out who the "spirit of arkham" is?Where is the last arkham chronicle located in the game batman: arkham asylum?
Go to the little "tower" near Clayface where you left the Warden. It's where you first got the ability to shut down the security gates.Where is the last arkham chronicle located in the game batman: arkham asylum?
where you found quincy sharp, the little tower in the middle of the room where clayface is at. on the floor in the little tower you will see a "donut" made of alot of different words and letters, hope this helped

scars