SUPERSTRING PERTURBATION THEORY AT TWO-LOOPS
      Duong H. Phong

References for Phong's talk:
  See S. Hollander, "A Homotopy theory for stacks",
  L. Mahe, J. Minac and T. Smith, "Additive structure of multiplicative subgroups of fields and Galois theory",
  C. Gordon and J.P. Rossetti, "Boundary volume and length spectra of Riemannian manifolds: what the middle degree Hodge spectrum doesn't reveal",
  D. Eisenbud and F.-O. Schreyer, "Resultants and Chow forms via exterior syzygies",
  M. Peletier, H. Westerhoff and B. Kholodenko, "Control of spatially heterogeneous and time-varying cellular reaction networks: a new summation law",
  N.B. Chau, "D-chtoucas de Drinfeld a modifications symetriques et identite de changement de base",
  S.E. Rao, "Toroidal Z-algebras",
and references therein.