Free field world-sheet correlators for AdS3

We employ the free field realisation of $\mathfrak{psu}(1,1|2)_1$ world-sheet theory to constrain correlators string on ${\rm AdS}_3\times {\rm S}^3\times \mathbb{T}^4$ with unit NS-NS flux. In particular, we directly obtain unusual delta function localisation these onto branched covers boundary S}^2$ by (genus zero) -- this is key property which makes equivalence dual symmetric orbifold manifest. our approach, feature follows from a remarkable `incidence relation' obeyed correlators, reminiscent twistorial description. also illustrate results explicit computations in various special cases.