[en] The author reviews the formulation of manifestly covariant relativistic statistical mechanics as the description of an ensemble of events in spacetime parameterized by an invariant proper time τ. He discusses the linear and cubic mass spectra which result from this formulation (the latter with the inclusion of anti-events) as the actual spectra of an individual hadronic multiplet and hot hadronic matter, respectively. These spectra allow one to predict the masses of particles nucleated to quasi-levels in such an ensemble. As an example, the masses of the ground state mesons and baryons are considered, the results are in excellent agreement with the measured hadron masses. Additivity of inverse Regge slopes is established and shown to be consistent with available experimental data on the D^* meson and Γ_c baryon production