SANDERSON BACK

Derek Sanderson, the Boston Bruins' flamboyant center who made $1 million in a brief fling in the new World Hockey Association, formally returned yesterday to the National Hockey League's defending but slumping Champions.

After a week of daily negotiations, plus medical examinations and stiff tests on the ice, Sanderson signed a two-year contract extending through the 1973-74 season for a reported $200,000.