Rob Lucci's initial Vivre Card has been changed from Learned Haki to strengthened Haki related to Rokushiki : r/OnePiece

One Piece: All Known Rokushiki Abilities, Ranked

Rankyaku, One Piece Role-Play Wiki

Why didn't Luffy learn Rokushiki techniques? - Quora

What power is it? : r/OnePiece

Which do you prefer in One Piece, Devil Fruit, Haki or Rokushiki? - Quora

Rokushiki/Tekkai, One Piece Wiki

Advanced Six Powers Techniques - One Piece Theory

One Piece: 6 poderes mais fortes que não são Haki

One Piece: 10 Characters You Never Knew Possessed Haki

Why aren't there more characters who uses Rokushiki? Like if you spend your whole life being a swimming champion only to have to eat a Devil Fruit that throws away those years