SB 4.13.2

vidura uvāca
ke te pracetaso nāma
 kasyāpatyāni suvrata
kasyānvavāye prakhyātāḥ
 kutra vā satram āsata
Word for word: 
viduraḥ uvāca — Vidura inquired; ke — who were; te — they; pracetasaḥ — the Pracetās; nāma — of the name; kasya — whose; apatyāni — sons; su-vrata — O Maitreya, who have taken an auspicious vow; kasya — whose; anvavāye — in the family; prakhyātāḥ — famous; kutra — where; vā — also; satram — the sacrifice; āsata — was performed.
Translation: 
Vidura inquired from Maitreya: O greatly advanced devotee, who were the Pracetās? To which family did they belong? Whose sons were they, and where did they perform the great sacrifices?
Purport: 

The great Nārada’s singing, in the previous chapter, of three verses in the sacrificial arena of the Pracetās gave another impetus to Vidura to ask further questions.