The designations employed and the presentation of the material in this publication do not imply
the expression of any opinion whatsoever on the part of the World Health Organization concerning
the legal status of any country, territory, city or area or of its authorities, or concerning the
delimitation of its frontiers or boundaries. Dotted lines on maps represent approximate border
lines for which there may not yet be full agreement.
The mention of specific companies or of certain manufacturers’ products does not imply that
they are endorsed or recommended by the World Health Organization in preference to others of
a similar nature that are not mentioned. Errors and omissions excepted, the names of proprietary
products are distinguished by initial capital letters.
All reasonable precautions have been taken by the World Health Organization to verify the
information contained in this publication. However, the published material is being distributed
without warranty of any kind, either expressed or implied. The responsibility for the interpretation
and use of the material lies with the reader. In no event shall the World Health Organization
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