Thornadtsson , A., N. Drca, F. Ricciardolo, and M. Högman. “Increased Levels of Alveolar and Airway Exhaled Nitric Oxide in Runners”. Upsala Journal of Medical Sciences, vol. 122, no. 2, May 2017, pp. 85–91, doi:10.1080/03009734.2017.1317886.