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We argue with Kryachko's criticism [Int J Quantum Chem 2005, 103, 818] of the original proof of the second Hohenberg-Kohn theorem. The Kato cusp condition can be used to refute a "to-be-refuted" statement as an alternative to the original proof by Hohenberg and Kohn applicable for Coulombic systems. Since alternative ways to prove falseness of the "to-be-refuted" statement in a reduction ad absurdum proof do not exclude each other, Kryachko's criticism is not justified. |