5Shin H J, Kwan J R, Song S J. Ultrasonic Real Time Imaging Technique for the Inspection of Electrofusion Joints for Polyethylene Piping[C]. 2001 Forum for Gas Safety. Korea: Korea Gas Safety Corporation, 2001.
6Addison R C Jr, Safaeinili A, McKie A D W. Laserbased ultrasound for the Inspection of gas pipelines [J]. Nondestructive Evaluation, 1997,16 : 1277- 1281.