pan>
                     <span class="Comment">## </span>
                     <span class="Comment">## 		       NOTE: when debugging, do *not* set side = 3,</span>
                     <span class="Comment">## 		       but rather to the kind of numerical derivative</span>
                     <span class="Comment">## 		       you want to compare the user-analytical one to</span>
                     <span class="Comment">## 		       (0, 1, -1, or 2).</span>
                     <span class="Comment">## </