to recall; to look back upon

to go upstream; to trace the source

to trace back to

to investigate the origin of sth; to trace a river upstream back to its source

river tracing; mountain stream climbing (recreational activity)

see 追根溯源[zhui1 gen1 su4 yuan2]

to go back to the source

to trace sth back to its origin

to pursue sth back to its origins; to trace back to the source; to get to the bottom of sth

to go back to the source