The World Health Organization says it needs to see clear evidence of sustained community transmission of the swine flu virus from person-to-person in at least two regions of the world before it raises its alert to the phase six pandemic level.

VOA: standard.2009.05.14

Phase Two, in the middle Pleistocene phase--700,000 years ago.

第二阶段,在更新世的中期,约七十万年前

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

Phase Two, in the middle Pleistocene phase--700,000 years ago.

第二阶段,在更新世的中期,约七十万年前

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选