1. 4. L Ingvarsson, K Lundgren, B Olofsson, and S. Wall, Epidemiology of acute otitis media in children . Acta Otolaryngol (Stockh)1982 ; Suppl 388.
2. 5. M. F-Nicolaysen, Tympanometry and secretory otitis media . Acta Otolaryngol (Stockh)1983 ; Suppl 394.