1. GRI (Gas Research Institute). 2004. Functional specification - advanced controls for two-stroke cycle stationary engines revision 1. Contract No. 8343. Chicago, IL: Gas Research Institute.
2. PRCI. 1997. Enhanced monitoring guidelines for IC engine parameter based compliance monitoring systems, prepared for the compressor research advisor committee of PRCI and the gas research institute. Contract No. PR-239-9439, Final Report. Chantilly, VA: Pipeline Research Council International.
3. PRCI. 2017b. Parametric emissions monitoring system plan for nitrogen oxides, revision 12c. Chantilly, VA: Pipeline Research Council International, Inc.