Upper limits on the equivalent width of emission lines in the afterglow of GRB 120711A in the case of narrow (ΔE = 0 eV, solid curve) or wide (ΔE = 200 eV, dotted curve) lines. The curves give the best fit (with a 4th-order logarithmic polynomial) to the values obtained from simulations. For comparison, the rest-frame equivalent widths reported for other GRBs are also plotted: ◯ GRB 970828, ▽ GRB 970508, + GRB 991216, ∗ GRB 000214, △ GRB 001025, squares GRB 010220, filled diamond GRB 011211, × GRB 020813, and ♢ GRB 030227. The energies corresponding to the transition n = 2 → 1 for some H-like ions are also indicated.