Davis KH, Su J, Gonzalez JM, Trudeau JT, Nelson LM, Hauber B, Hollis KA. Quantifying the importance of inhaler attributes corresponding to items in the patient satisfaction and preference questionnaire in patients using Combivent Respimat. Health Qual Life Outcomes. 2017 Oct 16;15(1):201. doi: 10.1186/s12955-017-0780-z