^Mircea Eliade, John C. Holt, Patterns in comparative religion, 1958, p. 94. The connection of dingir and Old Turkic tengere was made by F. Hommel in Grundriss der Geographie und Geschichte des alten Orients (1928).
P. A. Barton in Semitic and Hamitic Origins (1934) suggested that the Mesopotamian sky god Anu may have been imported from Central Asia to Mesopotamia.
The similarity of dingir and tengri was noted as early as 1862 (i.e. during the early phase of the decipherment of the Sumerian language, before even the term Sumerian had been coined to refer to it), by George Rawlinson in his The Five Great Monarchies of the Ancient Eastern World (p. 78).