Devereux, G., Cotton, S., Barnes, P., Briggs, A., Burns, G., Chaudhuri, R., Chrystyn, H., Davies, L., De Soyza, A., Fielding, S., Gompertz, S., Haughney, J., Lee, A. J., McCormack, K., McPherson, G., Morice, A., Norrie, J., Sullivan, A., Wilson, A., & Price, D. (2015). Use of low-dose oral theophylline as an adjunct to inhaled corticosteroids in preventing exacerbations of chronic obstructive pulmonary disease: Study protocol for a randomised controlled trial. Trials, 16(1), Article 267. https://doi.org/10.1186/s13063-015-0782-2