Baker and Blackwell, May 2001, Adult and infant vocalization: speaking valves used in individuals with tracheostomy and ventilator dependency
Reference
Baker, B. M. and
Blackwell, P. B.
Adult and infant vocalization: speaking valves used in individuals with tracheostomy and ventilator dependency. J KY Med Assoc, 99(5): 193-203. (2001).

