1. J. Shin, Statement before the Subcommittee on Space and Aeronautics, Committee on Science and Technology, U.S. House of Representatives, May 5, 2010.
2. R. Dinius, Statement before the Subcommittee on Space and Aeronautics, Committee on Science and Technology, U.S. House of Representatives, May 5, 2010.
3. http://volcanoes.usgs.gov/ash/properties.html.
4. http://en.wikipedia.org/wiki/Volcanic_ash#cite_note-wdr-22.
5. http://volcanoes.usgs.gov/images/pglossary/ash.php.