Published 1993 in Physical review. D, Particles and fields

As open N=2 or 4 strings describe self-dual N=4 super Yang-Mills in 2+2 dimensions, the corresponding closed (heterotic) strings describe self-dual un-gauged (gauged) N=8 supergravity. These theories are conveniently formulated in a chiral superspace with general supercoordinate and local OSp(8|2) gauge invariances. The super-light-cone and covariant-component actions are analyzed. Because only half the Lorentz group is gauged, the gravity field equation is just the vanishing of the torsion.

) 2574 ; A . Parkes , A cubic action for self - dual Yang - Mills , Zürich preprint ETH - TH / 92 - 14 ( March 1992 ) . [ 11 ] A . D ’ Adda and F . Lizzi