1 C.. Hackman, J.. Levine, T.E. Parker, D.. Piester, and J.. Becker, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control 53, (2006).
1 C.. Hackman, J.. Levine, T.E. Parker, D.. Piester, and J.. Becker, in (IEEE, Montreal, Canada, 2004).
and 
