what is the main common interests of the nur ad-din al-bitruji and ahmad ibn muhammad ibn kathir al-farghani ?
SELECT DISTINCT var_uri where brack_open dbr_Nur_ad-Din_al-Bitruji dbp_mainInterests var_uri sep_dot dbr_Ahmad_ibn_Muhammad_ibn_Kathir_al-Farghani dbp_mainInterests var_uri brack_close