Detection of axial cracks in pipes using focused guided wavesFletcher, Sam; Lowe, Michael John Stewart; Ratassepp, Madis; Brett, ColinJournal of nondestructive evaluation2012 / p. 56-64 : ill https://www.researchgate.net/publication/234956324_Detection_of_Axial_Cracks_in_Pipes_Using_Focused_Guided_Waves