Behavior of lithium abundances as a function of effective temperatures for NGC 4590, NGC 6809, and NGC 6656, from top to bottom panels. Left panels: abundances (black points) and upper limits (blue arrows). Right panels: measurements in gray and the binned Li abundances, considering equal-sized bins (blue points). Red squares mark the bins considered to be part of the Li LRGB plateau and used to calculate mean values reported.