van der Werff, Ross, Shaun O’Leary, Gwendolen Jull, Michael Peolsson, Johan Trygg, and Anneli Peolsson. 2014. “A Speckle Tracking Application of Ultrasound to Evaluate Activity of Multilayered Cervical Muscles”. Journal of Rehabilitation Medicine 46 (7):662-67. https://doi.org/10.2340/16501977-1822.