SL(2,R)-invariant IIB Brane Actions
  We give a universal SL(2,R)-invariant expression for all IIB p-brane actions with p=-1,1,3,5,7,9. The Wess-Zumino terms in the brane actions are determined by requiring (i) target space gauge invariance and (ii) the presence of a single Born-Infeld vector. We find that for p=7 (p=9) brane actions with these properties only exist for orbits that contain the standard D7-brane (D9-brane). We comment about the actions for the other orbits. 
Eric A. Bergshoeff, Mees de Roo, Sven F. Kerstan, Tomas Ortin, Fabio   Riccioni