Class and Level Geekery VIII (spoilers ahoy!)

[Psyren]

Each of those is a one-off occurrence of "this specific thing from this book got used", not a general "this book is in common use and everything in it will be used without comment from now on".

I never attempted to state otherwise. I was listing books that the Giant took something from. If nothing else, it shows which books he's read before writing {strip.}

Anything can be used if it is explicitly referenced. That has never been in question. The "which books are available" thing is about which books we should assume are being used when no explicit reference is present.

I provided a potential list of those above the post you quoted; the other three are for completeness.