There are many pages on the Internet that provide Pokemon info. Some are more reliable and in-depth than others. The following hyperlinks are arranged from most reliable to least reliable. A referee should consider a higher placed website's information correct if it contradicts a lower placed website's information, unless there is reasonable doubt that it is wrong in that specific case. Please look at the notes beside each source.
The Ultimate Pokemon Center
URPG's Reffing Encyclopedia
You can use the URPG's official Pokédex - The Ultra Dex
- to verify if a Pokémon truly learns a move, or for other purposes.
The reffing calculator is a ref's most important tool, hopefully for obvious reasons. Here is a list of calculators for the URPG.
'New' Reffing Calc
'Old' Reffing Calc
Credit towards making the Reffing Calc goes to the user Pikachu. Credit also goes to DaRkUmBrEoN, Monbrey, Espeon, and WebMaster for updating and adding on to the calculator. Credit for the FFA Calc goes to Elrond. Do note that the FFA Calc and 'Old' Reffing Calc perform calculations that are off by 1-4 HP.