Friedrich, P. (1970). Proto-Indo-European trees: The arboreal system of a prehistoric people. University of Chicago Press.
Chicago-viite (17. p.)Friedrich, Paul. Proto-Indo-European Trees: The Arboreal System of a Prehistoric People. Chicago: University of Chicago Press, 1970.
MLA-viite (8. p.)Friedrich, Paul. Proto-Indo-European Trees: The Arboreal System of a Prehistoric People. University of Chicago Press, 1970.
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