"The courts have repeatedly told appellants that it is not acceptable to comb through a set of reasons for hints of error and fragments of mistake, and to try to assemble these into a case for oversetting the decision. No more is it acceptable to comb through a patently deficient decision for signs of the missing elements, and to try to amplify these by argument into an adequate set of reasons. Just as the courts will not interfere with a decision, whatever its incidental flaws, which has covered the correct ground and answered the right questions, so they should not uphold a decision which has failed in this basic task, whatever its other virtues."