A.T. Robertson Commentary Acts 19:15

"And the evil spirit answered and said unto them, Jesus I know, and Paul I know, but who are ye?" — Acts 19:15 (ASV)

Jesus I know (τον Ιησουν γινωσκω). "The (whom you mention) Jesus I recognize (γινωσκω)" and "the (whom you mentioned) Paul I am acquainted with (τον Παυλον επισταμα)." Clear distinction between γινωσκω and επισταμα.

But who are ye? (υμεις δε τινες εστε?). But you, who are you? Emphatic prolepsis.