Many Gaudiya Vaisnava acaryas have quoted verses from the Narada-pancaratra in their own works. Verses from the Narada-pancaratra have been quoted in the Bhakti-rsamrta-sindhu (1.2.11 and 13), the Laghu-bhagavatamrta (verse 147) and thirty-one times in the Hari-bhakti-vilasa. The principal subject matter of this literature is Sri Krsna and it contains various names, mantras, prayers and kavacas related to Sri Radha-Krsna. Vaisnava-dharma is the oldest religion. Indeed, worship of Lord Visnu is the eternal constitutional duty of all living entities. The Vaisnava Religion is elaborately described in the Bhagavad-gita and the Srimad-Bhagavatam. Vaisnava-dharma is also propagated in the Upanisads, wherein devotional service, which is the life and soul of Vaisnava-dharma, has been described in the form of codes.