1. Long term observation of RC-bridge using changes in natural frequencies;Askegaard;Nordic Concrete Research,1988
2. Astridge , D.G. 1985 The health and usage monitoring of helicopter systems - the next generation
3. Baumann , E.W. Becker , R.S. Ellerbrock , P.J. Jacobs , S.W. 1997 DC-XA Structural Health Monitoring System
4. Begg , R.D. Mackenzie , A.C. Dodds , D.J. Loland , O. 1976 Structural integrity monitoring using digital processing of vibration signals