Flux-flux relations between Hα and Ca ii IRT lines (λ 8498, λ 8542, and λ 8662 Å, from the left to the right, respectively). The meaning of the symbols is as in Fig. 10. The full red lines are the least-squares regressions, whose coefficients are reported in Eq. (2). The dashed lines represent the best fits of flux-flux relations found by Stelzer et al. (2013) for Class III objects. Downward and leftward arrows indicate upper limits on Hα and Ca ii fluxes, respectively.