user: Question: name the Sorority a.k.a. "Sigmas" that was founded in the University of Southern California.
Columns: ['Letters', 'Organization', 'Nickname', 'Founding Date', 'Founding University', 'Type']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['αΚΔΦ', 'alpha Kappa Delta Phi 1', '"KDPhi"', '1990-02-07', 'University of California, Berkeley', 'Sorority']
SQL:

assistant: SELECT "Organization" FROM "Table" WHERE "Founding University" = 'University of Southern California' AND "Type" = 'Sorority' AND "Nickname" = '"Sigmas"';