1. Specification No. NWG1 (Rev. 1): Procedural specification for limitation of noise in plant and equipment for use in the petroleum industry,1972
2. Specification No. NWG2 (Rev. 1): Equipment Vendor's Extract from NWG1
3. Publication No. NWG3 (Rev. 1): Purchaser's and Contractor's Guides to use of NWG1
4. Noise from Plant and Equipment—An Oil Industry Approach
5. ISO Recommendation R1996,1971