Lecker, Michael. «Were Customs Dues Levied at the Time of the Prophet Muḥammad?». Al-Qanṭara 22, no. 1 (junio 30, 2001): 19–43. Accedido agosto 9, 2022. https://al-qantara.revistas.csic.es/index.php/al-qantara/article/view/225.