  Closure relations satisfied by the radial Dirac-Coulomb Sturmians are proved
analytically. The Sturmian expansion of the Dirac-Coulomb Green function is
transformed to the form containing only series with summations running over
non-negative indices. The main paper was published in J. Phys. B: At. Mol. Opt.
Phys. 30 (1997) 825-61 [Erratum: 30 (1997) 2747], see also J. Phys. A: Math.
Gen. 31 (1998) 4963--90 [Erratum: 31 (1998) 7415-6].
