Generally recognised as the world's leading authority on modern Kurdish and medieval Khwarezmian, he also made distinguished contributions to the study of many other Iranian languages, including Pashto, Pahlavi and Sogdian, at the same time displaying enviable competence in non-Iranian languages such as Arabic and Chinese."
He is generally recognized as a leading authority on modern Kurdish and medieval Khwarezmian. He has also made significant contributions to the study of various Iranian languages like Pashto, Pahlavi, and Sogdian, while showcasing remarkable proficiency in non-Iranian languages such as Arabic and Chinese.