Lithium abundance as a function of mass for isochrones with ages estimated for each cluster. Contiunuous isochrones are from models with extra mixing and dotted isohrones from standard models. Magenta lines represent the isochrones for the Hyades with [Fe/H] = + 0.13 and ages of 0.79 Gyr and 0.69 Gyr, respectively; blue lines represent the isochrones for NGC 752 with [Fe/H] = + 0.00 and ages of 1.59 Gyr and 1.51 Gyr, respectively; and green lines represent the isochrones for M 67 with [Fe/H] = + 0.01 and ages of 3.87 Gyr and 3.60 Gyr, respectively.