Color–magnitude diagram of the open cluster NGC 752. Open circles are the whole sample of NGC 752 stars from Daniel et al. (1994). Filled black circles are our working sample of stars for which we have a lithium abundance estimation. Blue diamonds represent the known binaries of this sample. The continuous line is the isochrone of 1.59 Gyr calculated from our TGEC models with extra mixing and the dotted line is the isochrone of 1.51 Gyr calculated from standard models.