1. Laurent Bartholdi and Michael R. Bush, Maximal unramified 3-extensions of imaginary quadratic fields and SL2(Z3), J. Number Theory 124 (2007), no. 1, 159–166.[MR/arXiv]
  2. M. R. Bush, Computation of Galois groups associated to the 2-class towers of some quadratic fields, J. Number Theory 100 (2003), no. 2, 313–325.[MR]