20 Pa.C.S. § 764: Citation.

Jurisdiction of the person shall be obtained by citation to be awarded by the orphans' court division upon application of any party in interest. The citation shall direct the party named therein to file a complete answer under oath to the averments of the petition on or before a day certain, which shall be not less than ten days after the service thereof, and to show cause as the decree of the division shall provide.