The Relationship between Serum YKL-40 Levels and Severity of Asthma - Duru, Serap; Yüce, Gülbahar; Ulasli, Sevinc Sarinc; Erdem, Melike; Kizilgün, Murat; Kara, Fatma; Ardıc, Sadık (Iranian Journal of Allergy, Asthma and Immunology)