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We comment on the recent results of Refs. [1, 2] on the bipolaron problemderived using an approximation of Gross - Tulub. It is proved that, contrary tothe claim made in Refs. [1, 2], the bipolaron ground state energy calculatedthere in the strong-coupling approximation has not been shown to constitute avariational upper bound.

Comments on "Translation-invariant bipolarons and the problem of high-temperature superconductivity"