Shigan, Wiki

The Six Powers, Wiki

Could Mihawk or Shanks Know Rokushiki? : r/OnePiecePowerScaling

World of Shinjoin! — The Nico Robin: Rokushiki style Project! (part2)

Character Profile - Jyabura

Rokushiki (All) - Roblox

Chapter Discussion - Rokushiki is based on Haki, Page 7

Rokushiki/Shigan, OnePiece Fanon Wiki

Honestly Oda probably should have just expanded on Rokushiki instead of creating Haki. He could have definitely made it to where there are techniques that allow you to hit logias and armament

One Piece sound effects - Rokushiki/Shigan v1

One Piece: Robin uses Shigan on Giant Prisoner by SUSHIFREAK101 on DeviantArt