WITNESS

Risālah fī istikhrāj khaṭṭayn bayna khaṭṭayn ḥattá tatawālā al-arbaʿah ʿalá nisbah wa-qismat al-zāwiyah bi-thalāthah aqsām mutasāwiyyah_Cairo_Dār al-kutub_Muṣṭafā Fāḍil riyāḍa_40