Pokemon TCG Logic: Where Mewtwo can be a Dark type and have a weakness to Psychic : r/pokemon
How to Apply Weakness and Resistance in the Pokémon Card Game
Pokémon Type Chart - Strengths and Weaknesses - Xfire
Weakness Policy - SM - Burning Shadows - Pokemon
PrimetimePokemon's Blog: Pokemon Card of the Day: Flying Pikachu Reprint (Rising Rivals)
I created a SWSH Era Weakness and Resistance Chart. I'm 99.9% sure that these are accurate, but if you find any exception to these rules, feel free to comment and I will