Barbarito, N., and E. De Mattia. “Grading the Severity of Obstruction in Patients With Chronic Obstructive Pulmonary Disease and Morbid Obesity”. Monaldi Archives for Chest Disease 79, no. 3-4 (December 30, 2013). Accessed June 21, 2021. https://monaldi-archives.org/index.php/macd/article/view/11.