Barycentric orbital elements distribution of the TNOs that are close to the 3/1 MMR with Neptune. We show 76 bodies in the range [61, 64] au, with each colour corresponding to a different inclination range. The resonant TNOs are marked with a cross (Table 1), and the remaining non-resonant with a dot. The orange vertical line gives the nominal resonant semi-major axis a ≈ 62.55 au. The black solid and dashed lines give the overlap with Neptune and Uranus orbits, respectively.