Fryer, Gary and Fossum, Christian (2010) Therapeutic mechanisms underlying muscle energy approaches. In: Tension-type and cervicogenic headache : pathophysiology, diagnosis, and management. Fernández-de-las-Peñas, César, Arendt-Nielsen, Lars and Gerwin, Robert D, eds. Jones and Bartlett's contemporary issues in physical therapy and rehabilitation medicine series . Jones and Bartlett Publishers, Sudbury, Mass., USA, pp. 221-229.

Fryer, Gary and Fossum, Christian (2010) Muscle Energy techniques. In: Tension-type and cervicogenic headache: pathophysiology, diagnosis, and management. Fernández-de-las-Peñas, César, Arendt-Nielsen, Lars and Gerwin, Robert D, eds. Jones and Bartlett's contemporary issues in physical therapy and rehabilitation medicine series . Jones and Bartlett Publishers, Sudbury, Mass., USA, pp. 309-326.

Fossum, Christian and Fryer, Gary (2009) Cervical joint manipulative procedures. In: Tension-type and cervicogenic headache: pathophysiology, diagnosis, and management. Fernández-de-las-Peñas, César, Arendt-Nielsen, Lars and Gerwin, Robert D, eds. Contemporary Issues in Physical Therapy and Rehabilitation Medicine . Jones and Bartlett Publishers, Sudbury, Massachusetts, pp. 273-290.