DS-maps on the planes (a) (e₁, e₂) and (b) (ϖ₂, e₂) yielded by a periodic orbit (white cross) that belongs to the stable family (blue curve) of the configuration (θ₁, θ₂) = (0, 0). The dashed grey line depicts the region where the planetary collisions take place. The orbital elements of the periodic orbit that remain fixed during the computation of each map are noted down. The islands of stability showcase the following attributes: L: libration of all resonant angles and apsidal difference (MMR), L_S: secondary resonance, L_A: apsidal difference oscillation or circulation, and R: rotation of both resonant angles and apsidal difference.