Parker T.E., P. Hetzel, S.R. Jefferts, S. Weyers, L. Nelson, A. Bauch, and J. Levine, in (IEEE, Seattle, Wa, Usa, 2001).
Larson K.M., J. Levine, L.M. Nelson, and T.E. Parker, Ieee Transactions On Ultrasonics, Ferroelectrics And Frequency Control 47, 484-494 (2000).