This is sort of in response to this thread. What does it mean to have a reference, just have a proxy of the new card handy somewhere out of your deck? Or do you need a printed copy of an errata, etc?
You need to have an actual card outside of your deck for reference. Card scans aren't allowed, and I believe the Card-Dex is discontinued.
For example, if I used Base Set PlusPowers in my deck (and I sometimes do), I need to have a physical copy of PlusPower from Black & White outside my deck for reference.