1World Health Organization. The Weekly Epidemiological Record [EB/ OL]. Switzerland: World Health Organization, 2000. http://www.who. int/docstore/wer/75-27-52.html.
2World Health Organization. The Weekly Epidemiological Record [EB/OL]. Switzerland: World Health Organization, 2009. http://www.who. int/wer/2009/werSg40/en/index.html.