1. Handbook on non-destructive testing of concrete;Malhotra,1991
2. Ultrasonic testing of materials;Krautkramer,1990
3. Impact-Echo Non-Destructive Evaluation of Concrete and Masonry;Sansalone,1997
4. Wave Propagation in Structures;Doyle,1989
5. ACI 228.2R-98, Non-destructive Test Methods of Evaluation of Concrete in Structures, ACI Committee 228.