In Aitareya Brahmana (VIII.14), the Uttarakuru and the Uttaramadra tribes are stated to be living beyond Himalaya. Aitareya Brahmana also adduces these two people as an example of republican (vairajiya) janapadas or nations, where whole Janapada took the consecration of rulership. 
The Vamsa Brahmana (1/18) of the Sama Veda refers to Madrakara Shaungayani as the teacher of Aupamanyava Kamboja. Sage Shangayani Madrakara, as his name itself shows, and as the scholars have rightly pointed out, belonged to the Madra people. This connection between the Uttaramadras and the Kambojas is but natural, as they were close neighbors in the north-west (Vedic Index)).
From the fact that Kamboja Aupamanyava is stated to be pupil of sage Shangayani Madrakara, scholars like A. B. Keith and A. A. Macdonell of the Vedic Index as well as H. Zimmer and others postulate a possible connection of the Uttaramadras with the Kambojas who are stated to have had both Iranian as well as Indian affinities.
- Vedic Index, I. pp 84,138, II, p 61, A. B. Keith, A. A. Macdonnell,
- Geographical Data in Early Puranas, 1972, pp 65, 164, Dr M. R. Singh,
- History and Culture of Indian People, The Vedic Age, p 259.
- Some Kshatriya Tribes of Ancient India, 1924, p 231,
- Problems of Ancient India, 2000, p 6-7, K. D. Sethna.
- India as Known to Panini, p 50, Dr V. S. Aggarwala,
- cf also: An Ancient People of Panjab, The Udumbras, Journal Asiatique, 1926, p 11, Jean Przylusky showing that Bahlika (Balkh) was an Iranian settlement of the Madras who were known as Bahlika-Uttaramadras.
- tasmad atasyam udichya dishi ye ke ca pren himvantam janapada uttarakurva uttaramadra, iti vairajyaya te.abhishichyante, — (Aitareya Brahmana, VIII/14)