Kummer coverings -- Tamely ramified coverings of schemes -- Extension of some notions from the theory of schemes to the theory of formal schemes -- Tamely ramified coverings of formal schemes -- The tame fundamental group of a formal neighbourhood of an irreducible divisor -- Comparison of two 2-cohomology classes -- The tame fundamental group of a formal neighbourhood of an irreducible divisor (continued) -- Descent of tamely ramified coverings -- An application: the fundamental group of the spectrum of a complete local ring, of dimension two, minus a closed set