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."
Generally acknowledged as the world's foremost expert on modern Kurdish and medieval Khwarezmian, he also made notable contributions to the study of numerous other Iranian languages, including Pashto, Pahlavi, and Sogdian, while demonstrating exceptional proficiency in non-Iranian languages such as Arabic and Chinese.