Fatemah Ayatollah Zadeh Shirazi,  Amir Fallahpour,  Mohammad Reza Mardanbeigi & Zahra Nili Ahmadabadi. (1970). On Proximal Relations in Transformation Semigroups Arising from Generalized Shifts.
            <i>Analysis in Theory and Applications</i>. <i>38</i> (1).
            110-120.
         doi:10.4208/ata.OA-2017-0063