621—4.1 (20) General procedures.
	 4.1(1) Separate or combined petitions. Request for bargaining unit determination and bargaining representative determination shall be by petitions which may be filed separately. Where a request has been made to a public employer to bargain collectively with a designated group of public employees and the board has not previously determined the bargaining unit, the petitions shall be filed jointly or on a combined form provided by the board.
	 4.1(2) Intervention and additional parties. See rule 2.4(20).
	 4.1(3) Withdrawal of petitions. Petitions may be withdrawn only with the consent of the board. Petitions withdrawn after the commencement of a hearing, or withdrawn after direction of an election where no hearing was conducted, may not be refiled by the withdrawing party for a period of six months following the board order permitting withdrawal.