hep-th/0404023 [abs, ps, pdf, other] :
Title: An Index for 2D field theories with large N=4 superconformal symmetry
Authors: Sergei Gukov, Emil Martinec, Gregory Moore, Andrew Strominger
hep-th/0406055
Title: Multiloop Amplitudes and Vanishing Theorems using the Pure Spinor Formalism for the Superstring
Authors: Nathan Berkovits (IFT/UNESP, Sao Paulo)