Optopalatograph (OPG): a new apparatus for speech production analysis. - Alan Wrench; Alan D. McIntosh; William J. Hardcastle (ICSLP, 1996)

Optopalatograph: development of a device for measuring tongue movement in 3D. - Alan Wrench; Alan D. McIntosh; William J. Hardcastle (EUROSPEECH, 1997)

Optopalatograph: real-time feedback of tongue movement in 3D. - Alan Wrench; Alan D. McIntosh; Colin Watson 002; William J. Hardcastle (ICSLP, 1998)