Dependence of the transition redshift z_t on the present-day value of the dark energy equation of state w₀ and the transition width Δ in the three models considered in this work. The top, middle and bottom panels correspond, respectively, to the Models B, C, and L described in the text – cf. respectively, Eqs. (7)–(12). In all panels the colourmap denotes the value of z_t corresponding to each pair of values of w₀ and Δ (we note that the colourmap and the ranges of w₀ and Δ are different in each panel) and some specific contours are also identified by black lines with white labels.