Efektivitas perjanjian perkawinan yang tidak didaftarkan terhadap pihak ketiga (Analisis Kasus Akta Perjanjian Perkawinan Nomor 000 Yang Dibuat Dihadapan Notaris XXX) = Effectiveness of a marriage agreement that is not registered to third parties (Case Analysis: Deed of Agreement No. 000 The Marriage Agreement Made In front of Notary XXX)