Brown, D., Hutchison, L., Donaldson, K., MacKenzie, S., Dick, C., & Stone, V. (2007). The effect of oxidative stress on macrophages and lung epithelial cells: The role of phosphodiesterases 1 and 4. Toxicology Letters, 168(1), 1-6. https://doi.org/10.1016/j.toxlet.2006.10.016