Aghdam Ahad Mehdizadeh: Square subgroup of an Abelian group. In: Acta scientiarum mathematicarum, (51) 3-4. pp. 343-348. (1987)
Aghdam Ahad Mehdizadeh: On the strong nilstufe of rank two torsion free groups. In: Acta scientiarum mathematicarum, (49). pp. 53-61. (1985)