Which sourcebooks can be used as the additional resource for AL PHB+1?

The Adventurers League Players Guide for Season 9 explains PHB+1 as follows:

Forgotten Realms characters can choose race and class options from the Player’s Handbook and one other resource—a rule called “PHB+1.” Additional resources include the following products:

• Elemental Evil Player’s Companion (EEPC)

• Sword Coast Adventurer’s Guide (SCAG)

• Volo’s Guide to Monsters (VGM)

• Xanathar’s Guide to Everything (XGE)1

• Mordenkainen’s Tome of Foes (ToF)2

• Locathah Rising(LR)*

Is “include” as used here intended to mean “are limited to”, or are these resources simply listed as examples of sourcebooks that may be used?

*: Locathah Rising is listed in v. 9.2 of the ALPG that I have on my computer. I don’t remember how I obtained it. The linked PDF is version 9.0 and does not list this resource.

What DnD Sourcebooks (or just sources in general) are considered official for gameplay purposes versus what isn’t? [on hold]

I know that there is something similar at This Question by @nitsua60, but I want to ask something a bit different. That question was asking about what is official, but I want to ask about what is often confused for being official in DnD 5e (For adventurer’s league play) because it is really confusing both me and someone that I am trying to introduce to the game sometimes. For example, Wayfinder’s guide to Eberron is technically official, and is on DnD beyond, but it is still only for play testing?)

So, basically, I am getting really confused by legality (rules-wise) of various sources for various purposes, so I would like to know what are some of the most common reasons why something might seem legal (in that it is legal for Adventurer’s League), but it really isn’t, and some examples to look out for.