Multi-institutional assessment of the Provox 2 voice prosthesis. - Ackerstaff,AH.; Hilgers,FJM.; Meeuwis,CA.; Velden,L van der.; Hoogen,FJA van den.; Marres,HAM.; Vreeburg,GCM.; Manni,JJ. (Arch Otolaryngol Head Neck Surg, 1999)