HR diagram showing the location of all the PTPS stars studied in this paper. Colors of points denote Li abundance. Red are the most Li-rich objects (the red stars denote the four most Li-rich giants). Stars denoted in blue have moderate Li level, and black is for Li-poor stars. Crosses denote stars with uncertain atmospheric parameters. The blue stripes denote the beginning of RGB. The gray area is LFB region, and green box denotes RGC. Evolutionary tracks from Bertelli et al. (2008) for 1 − 3 M_⊙ stars with solar metallicity are plotted as solid lines.