See definitions in Sec. [2BG]↺↻. We also define this notion.
[0RG]↺↻
[0RH]↺↻
[0RK]↺↻
[0RP]↺↻
[0RR]↺↻
[0RT]↺↻
[0RY]↺↻
[0RX]↺↻