Valmiki Ramayana 7.57.20
एवं विदेहराजश्च जनकः पूर्वको ऽभवत् ।मिथिर्नाम महातेजास्तेनायं मैथिलो ऽभवत्॥
evaṃ videharājaśca janakaḥ pūrvako 'bhavat |mithirnāma mahātejāstenāyaṃ maithilo 'bhavat ||
Our plain-language meaning of this verse is waiting for scholar review.
Open in the book