Siergiejko , Z., G. Siergiejko, D. Siergiejko, P. Siergiejko, A. Krupa, and E. Świebocka. “Bronchial Methacholine Challenge – the Current State of Knowledge”. Alergoprofil, Vol. 10, no. 4, Nov. 2014, pp. 9-15, https://www.journalsmededu.pl/index.php/alergoprofil/article/view/819.