Erratum
During the relabelling of Figure 1 an error was introduced. The correct figure appears below.
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Fig. 1. Chemical structure of the tetrasaccharide repeat units in the O-antigens of S. flexneri serotypes 1a and 1c. d-GlcNAc, N-acetylglucosamine; Rha, rhamnose.
The Press apologizes to the authors and readers for this error.