Section 8. Notice shall be given by a citation containing a brief description of the land, and the minimum price in case it is desired to sell the land or any part thereof at private sale. The citation shall be addressed to all known respondents by name, and, in addition, in express terms to all other persons interested. Said notice shall be given to each respondent, whether within or without the commonwealth, whose address is known, by serving the same, either personally or by registered mail, fourteen days at least before the return day; and to each respondent whose address is not known by mailing a copy thereof to the last known address of such party fourteen days at least before the return day, and by publishing the notice once in each of three successive weeks in such newspaper as the court shall order, the last publication to be one day at least before the return day. Proof of service and notice shall be made by affidavit, setting forth the particulars of the service on each respondent, and any other notice given, and if actual notice has been given by registered mail the affidavit shall so state. The court may in its discretion cause further notice to be given.