  Symmetry breaking perturbations in an electronically conducting medium are
known to produce Friedel oscillations (FOs) in various physical quantities of
an otherwise pristine material. Here we show in a mathematically transparent
fashion that FOs in graphene have a strong sublattice asymmetry. As a result,
the presence of impurities and/or defects may impact the distinct graphene
sublattices very differently. Furthermore, such an asymmetry an be used to
explain the recent observations that Nitrogen atoms and dimers are not randomly
distributed in graphene but prefer to occupy one of its two distinct
sublattices. We argue that this feature is not exclusive of Nitrogen and that
it can be seen with other substitutional dopants.
