GB, 1, 5, 25, 10.2 uṣṇikkakubbhyāṃ bhṛgvaṅgiraso jagatyā sāmāni kavayo vadanti //

JB, 1, 158, 8.1 uṣṇikkakubbhyāṃ vā indro vṛtrāya vajram udayacchad gāyatryos tiṣṭhan /

PB, 8, 5, 2.0 uṣṇikkakubbhyāṃ vā indro vṛtrāya vajraṃ prāharat kakubhi parākramatoṣṇihā prāharat tasmāt kakubho madhyamaṃ padaṃ bhūyiṣṭhākṣaraṃ parākramaṇaṃ hi tad abhisamauhat tasmād uṣṇiha uttamaṃ padaṃ bhūyiṣṭhākṣaraṃ puro gurur iva hi vajraḥ //