1. Torge, W., Gravimetry, de Gruyter, W., Ed., Berlin, New York, 1989.
2. International Vocabulary of Basic and General Terms in Metrology, JCGM, 2008.
3. Milton, M.J.T. and Quinn, T.J., Primary Methods for the Measurement of Amount of Substance, Metrologia, 2001, vol. 38, no. 4, pp. 289–296.
4. Torge, W., The Changing Role of Gravity Reference Networks, IAG Symp., 1998, vol. 119, pp. 1–10.
5. Boedecker, G., Activity Report 1995–1998, IGC Working Group 2: Gravity Standards, BGI Bulletin D’Information, 1998, no. 83, pp. 25–27.