Sandberg, J., Johnson, M. J., Currow, D. C., & Ekström, M. (2018). Validation of the dyspnea exertion scale of breathlessness in people with life-limiting illness. Journal of Pain and Symptom Management, 56(3), 430-435.e2. https://doi.org/10.1016/j.jpainsymman.2018.05.002