1. OGA policy statement – maintenance strategies on fiscal measurement systems 21.08.2015.
2. OGA, Guidance Notes for Petroleum Measurement, Issue 9.2: For Systems operating under the Petroleum (Production) Regulations, October 2015.
3. DonaldW. Wyatt, HowardT. Castrup. Managing Calibration Intervals. Available on 17.07 at: 〈http://www.isgmax.com/articles_papers/mgcalint.pdf〉.
4. OIML D 10, Guidelines for the determination of calibration intervals of measuring instruments. Edition 2007 (E), 2007.
5. David Deaver Calibration intervals, a manufacturer’s perspective. Available on 17.07 at: 〈http://assets.fluke.com/download/calibration/MSC2009_Deaver.pdf〉.