Imaginary quadratic fields with Cl_2(k) = (2,2,2)
  In this article we classify the complex quadratic number fields k with 2-class group of type (2,2,2) whose Hilbert 2-class fields have a 2-class group of rank 2, and then determine the length of their 2-class field towers. 
Elliot Benjamin, Franz Lemmermeyer, Chip Snyder