1. ‘Performance of ultrasonic therapy instruments’;Allen;Physiotherapy,1978
2. ‘Medical electrical equipment Part 2. Particular requirements for Safety. Section 2.5: Specification for Safety of Ultrasonic Therapy Equipment’;British Standards Institution,1985
3. ‘The use of ultrasound by physiotherapists in Britain, 1985’;ter Haar;Ultrasound in Medicine and Biology,1987
4. ‘Evaluation of ultrasound therapy devices’;Hekkenberg;Physiotherapy,1986
5. ‘A versatile force balance for ultrasound power measurement;Perkins;Physics in Medicine and Biology,1989