@inbook{1141733766, author={Daquan Xu}, editor={Hadzic, Admir}, title={Physics of Ultrasound}, booktitle={Hadzic's Textbook of Regional Anesthesia and Acute Pain Management, 2e}, publisher={McGraw-Hill Education}, address={New York, NY}, year={2017}, url={accessanesthesiology.mhmedical.com/content.aspx?aid=1141733766} }