Within fifteen days after notice that a petition has been directed to be heard by a referee has been served upon the adverse parties thereof, the referee shall fix a time and place for hearing the petition. The referee shall as soon as practicable within the limitations prescribed herein fix a time and a place for hearing the petition and serve upon all parties in interest a notice of the time and place of hearing, and shall serve upon the petitioner a copy of any answer of any adverse party. The hearing on any such petition shall be held within thirty-five days of the filing of the petition.
77 P.S. § 802