"Geographically, the Avesta has little to offer the quest for the homeland of the Indo-Aryans speakers—with one very important exception. In sharp contradistinction to the lack of any clear reference in the Vedic tradition to an outside origin, the Avesta does preserve explicit mention of an airiianam vaejo, the legendary homeland of the Aryans and of Zarathustra himself. The descriptions of this place, despite the fact that "it is revealed that Ohrmazd made [it] to be better than the other places and regions," speak of severe climatic conditions (Humbach 1991, 35). Gnoli (1980, 130) situates the airiiansm vaejo in the Hindu Kush because all the identifiable geographic references in the Avesta are of eastern Iran, south central Asia and, Afghanistan, with an eastern boundary formed by the Indus. There is no mention of any place north of the Sir Darya (the ancient Jaxartes), nor of any western Iranian place (Boyce 1992, 3). ... There are also identical names of rivers common to both Iran and India, such as the Iranian Harahvaiti and Haroyu, which correspond to the Indian Sarasvati and Sarayu (Sanskrit s = Iranian h). In and of themselves, all that can be said of this data is that these names could have been either transferred by incoming Indo-Aryan tribes from Iranian rivers to Indian ones, as is generally assumed, or by outgoing Indo-Iranian tribes from Indian rivers (although any transfer from Iran to India must have occurred before Iranian developed the h phoneme, since s can become h but never vice versa)."