The first, developed by Hutson and White and described in Elastic Wave Propagation in Piezoelectric Semiconductors Journal of Applied Physics, 33, page 40 , provides a coupling mechanism between phonons and electrons and leads to absorption and {TAIL ~ dispersion} of the acoustic wave by {HEAD ~ free charge carriers} 
The first , developed by Hutson and White and described in Elastic Wave Propagation in Piezoelectric Semiconductors Journal of Applied Physics , 33 , page 40 , provides a coupling mechanism between phonons and electrons and leads to absorption and { TAIL ~ dispersion } of the acoustic wave by { HEAD ~ free charge carriers }
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