%Date: Mon, 14 Oct 1996 14:16:16 EDT %From: Edward Witten The following has been pointed out about exercise 5 in problem set 2. (a) I omitted to state that a connection on the SO(n) bundle Q over M is part of the data. It is certainly needed later. (b) there is a slip in part (b) of the problem - it was meant to be said that the odd part of lambda is left-moving (as is implied correctly later in part (c) ) Extra credit to anyone who points out additional errors!