  We present analytical derivation of the closed-form expression for the dipole
magnetic shielding constant of a Dirac one-electron atom being in an arbitrary
discrete energy eigenstate. The external magnetic field, by which the atomic
state is perturbed, is assumed to be weak, uniform and time independent. With
respect to the atomic nucleus we assume that it is pointlike, spinless,
motionless and of charge Ze. Calculations are based on the Sturmian expansion
of the generalized Dirac- Coulomb Green function [R. Szmytkowski, J. Phys. B
30, 825 (1997); erratum 30, 2747 (1997)], combined with the theory of
hypergeometric functions. The final result is of an elementary form and agrees
with corresponding formulas obtained earlier by other authors for some
particular states of the atom.
