Minimum and maximum inclination allowed for libration trajectories as a function of the eccentricity of the planet. The black curves represent the correlation in absence of GR. The blue, green, and red curves in both panels show the extreme values of the inclination for eccentricity e₂ of 0.1, 0.5, and 0.8, respectively, when the GR effects are included. Moreover, we adopt a particle’s semimajor axis a₂ of 15 au and 25 au in the top and bottom panels, respectively. Finally, we consider a semimajor axis a₁ = 1 au for the planet in both panels.