Greetings, Apparently they generally agree that Avestan is a Northeastern Iranian language. However I have read that some used to hold that Avestan might be a transitional or even a proto form bridging between Northeastern and Northwestern Iranian languages. I need to know based on what arguments they come up with the notion that Avestan is a Northeastern Iranian language? I mean the arguments in terms of historical developments ( ts* > s "span-" ~ "dog"; dz* > z "zan-" ~ "know/give birth"; dw* > "dv"/"b" "dvara" ~ "door", "bitiya*?" ~ "second"; t > th "thraya-" ~ "thee", and so on-sorry for my probable orthographic or semantic mistakes in regard with the Avestan proper). Many thanks in advance.