Ellrod, G. (2005). Remote Sensing of Volcanic Ash. National Weather Association. Retrieved May 24, 2010.

埃尔罗德。G .，(2005年)，火山灰之遥测，美国国家气象协会，2010年5月24日检索。

youdao

The National Ready Mixed Concrete Association points out that using ash in cement is not a new idea.

全国混凝土制成品协会指出，在水泥中使用灰烬不是一个新想法。

youdao

The National Ready Mixed Concrete Association points out that using ash in cement is not a new idea.

VOA: special.2009.12.01

In a move backed by ASH, the National Childminding Association (NCA) has called for the reversal of government regulations which allow childminders to smoke in front of children if parents give permission.

BBC: Parents 'ignorant' of smoking risks