This page of The Last of Us game guide contains information on where to find the comic books in The Suburbs chapter. Those items are collectibles-secrets. Our walkthrough indicates the exact location of each artifact and pendant.
Comic #5 - Antiparticles
After you start this stage, go ahead until you find a shipwreck.
The comic is inside on the desk.
Comic #6 - Messenger Particle
This one can be found near the ice-cream truck standing on the street.
There are two houses with their doors open nearby. Enter the one that is not made of red brick and climb up to the first floor.
The Comic is in the toilet.