In the Western world, Persia (or one of its cognates) was historically the common name used for Iran. On the Nowruz of 1935, Reza Shah officially asked foreign delegates to use the Persian term Iran (meaning the land of Aryans in Persian), the endonym of the country, in formal correspondence. Subsequently, the common adjective for citizens of Iran changed from Persian to Iranian. In 1959, the government of Mohammad Reza Pahlavi, Reza Shah's son, announced that both "Persia" and "Iran" can be used interchangeably, in formal correspondence. However, the issue is still debated among Iranians. Etymology of Iran The name "Iran" is first attested in the Avesta as airyānąm (the text of which is composed in Avestan, an old Iranian language spoken in the northeastern part of Greater Iran, or in what are now Afghanistan, Turkmenistan, and Tajikistan). It reappears in the Achaemenid period where the Elamite version of the Behistun Inscription twice mentions Ahura Mazda as nap harriyanam "the god of the Iranians". The Modern Persian word Īrān () derives immediately from Middle Persian Ērān (Pahlavi spelling: ʼyrʼn), attested in a third century AD inscription that accompanies the investiture relief of the first Sassanid king Ardashir I at Naqsh-e Rustam. In this inscription, the king's Middle Persian appellation is ardašīr šāhān šāh ērān while in the Parthian language inscription that accompanies the Middle Persian one the king is titled ardašīr šāhān šāh aryān (Pahlavi: ... ʼryʼn) both meaning king of kings of Iranians. The gentilic ēr- and ary- in ērān and aryān derives from Old Iranian *arya- (Old Persian airya-, Avestan airiia-, etc.), meaning "Aryan", in the sense of "of the Iranians". This term is attested as an ethnic designator in Achaemenid inscriptions and in Zoroastrianism's Avesta tradition, and it seems "very likely" that in Ardashir's inscription ērān still retained this meaning, denoting the people rather than the empire. Notwithstanding this inscriptional use of ērān to refer to the Iranian peoples, the use of ērān to refer to the empire (and the antonymic anērān to refer to the Roman territories) is also attested by the early Sassanid period. Both ērān and anērān appear in 3rd century calendrical text written by Mani. In an inscription of Ardashir's son and immediate successor, Shapur I "apparently includes in Ērān regions such as Armenia and the Caucasus which were not inhabited predominantly by Iranians". In Kartir's inscriptions (written thirty years after Shapur's), the