Reference
1. Hilgers FJM, Ackerstaff AH, van As CJ, Balm AJM, van den Brekel MWM, Tan IB. Development and clinical assessment of a Heat and Moisture Exchanger with a multi-magnet automatic tracheostoma valve (Provox FreeHands HME) for vocal and pulmonary rehabilitation after total laryngectomy. Acta Otolaryngol (Stockh), 2003;123:91-99.