 Many famous Islamic scientists and philosophers during the time of the Abbasid caliphate were ethnic Persians who wrote their scholarly works in Arabic while continuing to write literary works and poetry in Persian - famous examples are Avicenna and Khayyam.The term Persian Arab is rarely used as a self-appellation.Most tend to identify more strongly as either Persian or Arab and consider themselves to be members primarily of one ethnic group, but at the same time being aware of their mixed background.