Data about the gases has been taken from the following sources:
Dollard, G. J., P. Dumitrean, S. Telling, J. Dixon and R. G. Derwent (2007), Observed trends in ambient concentrations of C2-C8 hydrocarbons in the United Kingdom over the period from 1993 to 2004, Atmos. Environ., 33, 2559-2569.
Grant, A., C. S. Witham, P. G. Simmonds, A. J. Manning and S. O'Doherty (2010), A 15 year record of high-frequency, in situ measurements of hydrogen at Mace Head, Ireland, Atmos. Chem. Phys., 10, 1203-1214.
Simmonds, P. G., et al. (2006), Global trends, seasonal cycles, and European emissions of dichloromethane, trichloroethene and tetrachloroethene from the AGAGE observations at Mace Head, Ireland, and Cape Grim, Tasmania, J. Geophys. Res., 111, D18304, doi: 10.1029/2006JD007082.
UNEP (United Nations Environment Program) (2003) 2002 Report of the Solvents, Coatings and Adhesives Technical Options Committee - 2002 Assessment (STOC 2002), edited by B. Ellis, UNEP Ozone Secretariat, Nairobi, Kenya.
WMO (World Meteorological Organisation) (2011), Scientific Assessment of Ozone Depletion: 2010, Global Ozone Research and Monitoring Project-Report No. 52, 516 pp., Geneva, Switzerland.