Refusal of application for certification
29Where an application for certification of an employee organization as a bargaining agent for a proposed bargaining unit has been refused by the Board, that employee organization shall not apply for certification as bargaining agent for the same or substantially the same proposed bargaining unit until at least six months have elapsed from the day on which the Board last refused such certification unless the Board is satisfied that the previous application was refused by reason only of a procedural or technical error or omission made in connection therewith.