Veda Samhita was orally composed in north-western India (Punjab) between 1500 and 1200 BCE, while book 10 of the Rig Veda, and the other Samhitas were composed between 1200 and 900 BCE more eastward, between the Yamuna and the Ganges rivers, the heartland of Aryavarta and the Kuru Kingdom (c. 1200 – c. 900 BCE). The "circum-Vedic" texts, as well as the redaction of the Samhitas, date to c. 1000–500 BCE. According to tradition, Vyasa is the compiler of the Vedas, who arranged the four kinds of mantras into four Samhitas (Collections). Chronology, transmission, and interpretation Chronology The Vedas are among the oldest sacred texts. The bulk of the Rigveda Samhita was composed in the northwestern region (Punjab) of the Indian subcontinent, most likely between 1500 and 1200 BCE, although a wider approximation of 1700–1100 BCE has also been given. The other three Samhitas are considered to date from the time of the Kuru Kingdom, approximately 1200–900 BCE. The "circum-Vedic" texts, as well as the redaction of the Samhitas, date to c. 1000–500 BCE, resulting in a Vedic period, spanning the mid 2nd to mid 1st millennium BCE, or the Late Bronze Age and the Iron Age. The Vedic period reaches its peak only after the composition of the mantra texts, with the establishment of the various shakhas all over Northern India which annotated the mantra samhitas with Brahmana discussions of their meaning, and reaches its end in the age of Buddha and Panini and the rise of the Mahajanapadas (archaeologically, Northern Black Polished Ware). Michael Witzel gives a time span of c. 1500 to c. 500–400 BCE. Witzel makes special reference to the Near Eastern Mitanni material of the 14th century BCE, the only epigraphic record of Indo-Aryan contemporary to the Rigvedic period. He gives 150 BCE (Patañjali) as a terminus ante quem for all Vedic Sanskrit literature, and 1200 BCE (the early Iron Age) as terminus post quem for the Atharvaveda. Transmission The Vedas were orally transmitted since their composition in the Vedic period for several millennia. The authoritative transmission of the Vedas is by an oral tradition in a sampradaya from father to son or from teacher (guru) to student (shishya), believed to be initiated by the Vedic rishis who heard the primordial sounds. Only this tradition, embodied by a living teacher, can teach the correct pronunciation of the sounds and explain hidden meanings, in a way