1. Yu. I. Aleksandrov and E. N. Korchagina,Izmeritel'naya Tekhnika, No. 5, 66 (1994).
2. E. A. Khatskevich, et al.,Abstracts for the Conference on Metrological Support to Billing for Energy Resources [in Russian], Gosstandard Rossii, VNIIMS, Moscow (1998), p. 52.
3. ISO 6976,Natural Gas: Calculating Heat of Combustion, Density, Relative Density, and Wobbe Number [in Russian].