Phase difference φ_Z1−φ_M1 (modulo 1) between the fundamentals of the fits of the measurements of ⟨ B_z ⟩ and ⟨ B ⟩ by functions of the forms given in Eqs. (16) or (17), against stellar rotation period. Open symbols: stars showing ⟨ B_z ⟩ reversal; filled symbols: stars in which ⟨ B_z ⟩ has a constant sign. Among the latter, stars with positive values of ⟨ B_z ⟩ are represented by dots, while triangles correspond to negative values of ⟨ B_z ⟩. For a fraction of the stars, the error bar is shorter than the size of the representative symbol. Shaded zones correspond to forbidden regions where representative points of stars with dipole-like fields are not expected to be found. We identified three stars that depart from this expected behaviour.