1. ISO 6976, International Standard (1996), Natural Gas—Calculation of Calorific Values, Density, Relative Density and Wobbe Index from Composition.
2. ISO TC 193/SC2/WG2, Draft International Standard DIS 15971-1 (1999), Natural Gas—Measurement of Properties, Combustion Properties, Part 1, Calorific Value.
3. M. Jaeschke, A.E. Humphreys, Standard GERG Virial Equation for Field Use, GERG Technical Monograph TM5 (1991) and Fortschritts-Berichte VDI, Reihe 6, No. 266 (1992).
4. K.E. Starling, J.L. Savidge, Compressibility Factors of Natural Gas and Other Related Hydrocarbon Gases, American Gas Association (A.G.A.) Transmission Measurement Committee Report No. 8, 2nd Edition, 1992 and Errata No. 1, June 1993.
5. P. Schley, R. Kleinrahm, W. Wagner, Feasibility Study for Alternative Determination of Energy Flow in Natural Gas Pipelines, Report by Ruhr-Universität Bochum, Chair of Thermodynamics, prepared for Ruhrgas AG, Germany and Nederlandse Gasunie, The Netherlands, June 1997.