Wikipedia states on sparse languages that
There is a Turing reduction (as opposed to the Karp reduction from Mahaney's theorem) from a NP-complete language to a sparse language iff NP $\subseteq$ P/poly.
Is that correct in that it is so far proven for an arbitrary Turing reduction and not a limited P-time reduction? (Could it be true for P-time reductions also, but maybe not proven so far?) It cites this without reference. What is a reference for this?