Found this,if it's of any use!
<a href="http://www.alpa.org/internet/alp/feb01p22.htm" target="_blank">www.alpa.org/internet/alp/feb01p22.htm</a>
[ 30 December 2001: Message edited by: gas path ]
There's a reference to their use about a quarter way down
[ 30 December 2001: Message edited by: gas path ]</p>