AdS_3 x S^3 x S^3 x S^1 Solutions of Type IIB String Theory
  We analyse a recently constructed class of local solutions of type IIB supergravity that consist of a warped product of AdS_3 with a seven-dimensional internal space. In one duality frame the only other non-vanishing fields are the NS three-form and the dilaton. We analyse in detail how these local solutions can be extended to globally well-defined solutions of type IIB string theory, with the internal space having topology S^3 x S^3 x S^1 and with properly quantised three-form flux. 
Aristomenis Donos, Jerome P. Gauntlett, James Sparks