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.