the "true" exchange variation begins with 4.bd3 nc6 5.c3 nf6 6.bf4 bg4 7.qb3. it was was tried by bobby fischer. the position is equal. some of the strategic ideas are silimar to the queen's gambit declined, exchange variation, (1.d4 d5 2.c4 e6 3.nc3 nf6 4.cxd5 exd5) with colours reversed.