Bloem, Ada, Marcel Veltkamp, Martijn A. Spruit, Jan W.H. Custers, Eric W.P. Bakker, Hanneke M. Dolk, and Jan C. Grutters. 2018. “Validation of 4-Meter-Gait-Speed Test and 5-Repetitions-Sit-to-Stand Test in Patients With Pulmonary Fibrosis: A Clinimetric Validation Study”. Sarcoidosis Vasculitis and Diffuse Lung Disease 35 (4), 317-26. http://mattioli1885journals.com/index.php/sarcoidosis/article/view/7035.