How to search the "Referring User" based on "Referred User"?

Hi,

Greetings,

For instance A refers B, B creates an account via A's link. Based on the Referrals Summary, I could click "details" link to check the all the "Referred User" of A, in this case is B. We search "Referred User" based on "Referring User".

However, how could search the "Referring User" based on "Referred User"? Meaning, if I want to know the "Referring User" of B, which is A, then how shall I check it?

Thanks.