In 1966, Milnor surveyed in this Bulletin [23] the concept of Whitehead torsion, focusing on the definition, topological significance and computation of Whitehead groups and their relationship to algebraic ^-theory and the congruence subgroup problem. As Milnor showed in that survey [23, Appendix 1], an affirmative solution to the congruence subgroup problem for algebraic number fields would im...
