回溯

回溯	huí sù	to recall / to look back upon
回	Huí	Hui ethnic group (Chinese Muslims)
回	huí	to go back; to return; to turn back; to turn around / to reply; to answer / classifier for literary divisions (acts of a play, sections or chapters of a classic book) / classifier for occurrences or times
回	huí	to curve / to return / to revolve
回	huí	variant of 回
溯	sù	to go upstream / to trace the source
溯	sù	variant of 溯