In volume 9 part 9, Tsuji says, "Maybe Peter Carol’s pentagram ritual... No, maybe it needs to be more abstract than that." His name is Peter Carroll, not Peter Carol. He wrote Liber Null and Liber Kaos and he was one of the founders of the Illuminates of Thanateros. He's a niche figure, so I understand not knowing about him, but he is a specific real guy who's surname is spelled with two rs and two ls.