Selfduality of non-linear electrodynamics with derivative corrections
  In this paper we investigate how electromagnetic duality survives derivative corrections to classical non-linear electrodynamics. In particular, we establish that electromagnetic selfduality is satisfied to all orders in $\alpha'$ for the four-point function sector of the four dimensional open string effective action. 
W. A. Chemissany, Joost de Jong, Mees de Roo