Kelly, F., Armstrong, B., Atkinson, R., Anderson, H. R., Barratt, B., Beevers, S., et al. (2011). The London low emission zone baseline study. Res Rep Health Eff Inst.
Quint, J. K., Moore, E., Lewis, A., Hashmi, M., Sultana, K., Wright, M., et al. (2018). Recruitment of patients with Chronic Obstructive Pulmonary Disease (COPD) from the Clinical Practice Research Datalink (CPRD) for research. NPJ Prim Care Respir Med. http://doi.org/10.1038/s41533-018-0089-3