赫梯語
In recognizing the Hittite language as Indo-European on the basis of two letters found in Egypt ("Die zwei Arzawa-Briefe", 1902), he played an important role in the deciphering of the Hittite language script. In two landmark volumes (1907 and 1915) he published the Amarna letters, diplomatic correspondence of the reign of Pharaoh Amenhotep IV, better known as Akhenaten (1351–1334 BCE).