This page of The Last of Us game guide contains information on where to find the comic books in Tommy's Dam chapter. Those items are collectibles-secrets. Our walkthrough indicates the exact location of each artifact and pendant.
Comic #7 - Foreign Element
After you reach the brook, you will reach a place where you will have to climb up again.
Turn right, and at the car wreck you will find the comic.
Comic #8 - Zero Point
Inside the building at the abandoned ranch, climb up the stairs and turn left.
The comic is lying at the window.