Complex sentence: Aitareya Brahmana makes first reference to "Uttarakuru" and Uttaramadra as real-life Janapadas and informs us that these two nations lied beyond the Himalaya ranges (Hindukush).
Split into simpler sentences: Aitareya Brahmana makes first reference to "Uttarakuru" and Uttaramadra as real-life Janapadas. According to Aitareya Brahmana, these two nations lied beyond the Himalayan ranges (Hindukush).