Comment on ‘Structural properties and electrical resistivity of Na-substituted lanthanum manganites: La1−xNaxMnO3+y (x = 0.1, 0.125 and 0.15)’ and ‘Structure and electrical resistivity of La1−xBaxMnO3 (0. 25 ≤ x ≤ 0.35) perovskites’