The analysis of the Mn-chalcogen atom (Te, Se, S) bond lengths in Mn-based A(II)-B-VI and A(IV)-B-VI metal chalcogenides (derived from X-ray absorption fine structure studies) as well as in Mn chalcogenides (from X-ray diffraction (XRD)) enabled the author to introduce certain self-corrections into the papers [Chem. Phys. Lett. 283 (1998) 313; Chem. Phys. Lett. 336 (2001) 226]. In particular, it was found that both the tetrahedral- and octahedral covalent radii of manganese depend on a choice of the anion species in the Mn-chalcogen atom bond, and therefore they cannot be considered as the element constants for Mn.