Towards single-valued polylogarithms in two variables for the   seven-point remainder function in multi-Regge-kinematics
  We investigate single-valued polylogarithms in two complex variables, which are relevant for the seven-point remainder function in N=4 super-Yang-Mills theory in the multi-Regge regime. After constructing these two-dimensional polylogarithms, we determine the leading logarithmic approximation of the seven-point remainder function up to and including five loops. 
Johannes Broedel, Martin Sprenger, Alejandro Torres Orjuela
hep-th