1. Specification No. NWG-1 (Revision 1): Procedural specification for limitation of noise in plant and equipment for use in the petroleum industry,1972
2. Specification No. NWG-2 (Revision 1): Equipment vendor's extract from NWG-1,1972
3. Publication No. NWG-3 (Revision 1): Purchaser's and contractor's guides to the use of Specification NWG-1,1972
4. Noise reduction;Beranek,1960