1. Oticon Polska Sp. z o.o., Aleja Jana Pawła II 22, 00-133 Warsaw, Poland
2. Department of Pediatric Otolaryngology, Centre of Postgraduate Medical Education, 01-813 Warsaw, Poland
3. Department of Pediatric ENT, The Children’s Hospital in Dziekanow Lesny, 05-092 Dziekanow Lesny, Poland
4. ACS Audika Sp. z o.o., 00-133 Warsaw, Poland