1. M.R. Clark, R. Gillespie, T. Kemp, D.M. McCann, M.C. Forde, Electromagnetic properties of railway ballast, NDT & E Int. 34 (2001) 305–311.
2. E.T. Selig, B.I. Collingwood, S.W. Field, “Causes of fouling in track”, AREA Bulletin, 71, 1998
3. EN 13450:2002/AC:2004. Aggregates for railway ballast. European Committee for Standardization, 2004.
4. EN 933-1:2012. Tests for geometrical properties of aggregates - Part 1: Determination of particle size distribution - Sieving method. European Committee for Standardization, 2012.
5. EN 933-4:2008. Tests for geometrical properties of aggregates - Part 4: Determination of particle shape - Shape index. European Committee for Standardization, 2008.
6. EN 1097-2:2010. Tests for mechanical and physical properties of aggregates - Part 2: Methods for the determination of resistance to fragmentation. European Committee for Standardization, 2010.
7. EN 1097-6:2013. Tests for mechanical and physical properties of aggregates - Part 6: Determination of particle density and water absorption. European Committee for Standardization, 2013.
8. EN 1097-3:1998. Tests for mechanical and physical properties of aggregates - Part 3: Determination of loose bulk density and voids. European Committee for Standardization, 1998.
9. CEN ISO/TS 17892-1:2014. Geotechnical investigation and testing - Laboratory testing of soil - Part 1: Determination of water content (ISO 17892-1:2014). European Committee for Standardization, 2014.
10. ASTM D4318-10e1. Standard Test Methods for Liquid Limit, Plastic Limit, and Plasticity Index of Soils, ASTM International, West Conshohocken, PA, 2010.
11. American Association of State Highway and Transportation Officials (AASHTO) 2011. Roadside Design Guide, 4th edn. AASHTO, Washington, DC.
12. EN ISO 17892-3:2015. Geotechnical investigation and testing - Laboratory testing of soil - Part 3: Determination of particle density (ISO 17892-3:2015, Corrected version 2015-12-15). European Committee for Standardization, 2015.
13. A. Benedetto, L. Pajewski, Civil Engineering Applications of Ground Penetrating Radar, Springer Transactions in Civil and Environmental Engineering Book Series, 2015.
14. D. Goodman, Ground-penetrating radar simulation in engineering and archaeology, Geophysics, 59 (2) (1994) 224-232.
15. F. Tosti, L. Pajewski, Applications of radar systems in Planetary Sciences: an overview, Chapt. 15 – Civil Engineering Applications of Ground Penetrating Radar, Springer Transactions in Civil and Environmental Engineering Book Series, pp. 361–371, 2015.4-232, 1994.
16. J.J. Schultz, M.E. Collins A.B. Falsetti, Sequential monitoring of burials containing large pig cadavers using ground-penetrating radar, J. Forensic Sci. 51 (3) (2006) 607-616.
17. R. Roberts, A. Schutz, I.L. Al-Qadi, E. Tutumluer, Characterizing railroad ballast using GPR: recent experiences in the United States, in Proc. of the 2007 4th International Workshop on Advanced Ground Penetrating Radar (IWAGPR 2007), Naples, Italy, Jun. 2007.
18. Railway Track and Structures Magazine, June 1985.
19. J. Hugenschmidt, Railway track inspection using GPR, Journal Appl. Geophys., 43 (2-4) (2000) 147–155.
20. G.R. Olhoeft, E.T. Selig, Ground penetrating radar evaluation of railroad track substructure conditions, in Proc. 9th International Conference on Ground Penetrating Radar (GPR 2002), Santa Barbara, USA, Apr. – May 2002.
21. Z. Leng, I.L. Al-Qadi, Railroad ballast evaluation using ground-penetrating radar, Transp. Res. Rec. 2159 (2010) 110–117.
22. F. De Chiara, Improvement of railway track diagnosis using Ground Penetrating Radar, PhD Thesis, 2014.
23. I.L. Al-Qadi, S. Zhao, P. Shangguan, Railway ballast fouling detection using GPR data: introducing a combined time–frequency and discrete wavelet techniques, Near Surf. Geophys. 14 (2) (2016) 145-153.
24. I.L. Al-Qadi, W. Xie, R. Roberts, Scattering analysis of ground-penetrating radar data to quantify railroad ballast contamination, NDT & E Int. 41 (6) (2008) 441-447.
25. H. Jol, “Ground Penetrating Radar”, Book, Ed. Elsevier, 2009.
26. D. Li, J. Hyslip, T.R. Sussmann, S. Chrismer, Railway geotechnics, Ed. Taylor and Francis, 2015.
27. T.R. Sussmann, M. Ruel, S. Christmer, Sources, influence, and criteria for ballast fouling condition assessment. In: Proceeding of the 91st Annual Meeting of the Transportation Research Board, 11 pp, 2012.
28. F. Tosti, C. Patriarca, E.C. Slob, A. Benedetto, S. Lambot, Clay content evaluation in soils through GPR signal processing, J. Appl. Geophys. 97 (2013) 69–80.
29. F. Tosti, A. Benedetto, L. Bianchini Ciampoli, S. Lambot, C. Patriarca, E.C. Slob, GPR analysis of clayey soil behaviour in unsaturated conditions for pavement engineering and geoscience applications, Near Surf. Geophys. 14 (2) (2016) 127-144.
30. B. Indraratna, L.J. Su, C.A. Rujikiatkamjorn, A new parameter for classification and evaluation of railway ballast fouling, Can. Geotech. J., 48 (2) (2011) 322-326.
31. N. Tennakoon, B. Indraratna, C. Rujikiatkamjorn, S. Nimbalkar, T. Neville, The role of ballast-fouling characteristics on the drainage capacity of rail substructure, Geotech. Test. J., 35 (4) (2012) 1-12.
32. L. Pajewski, F. Tosti, W. Kusayanagi, Antennas for GPR Systems, Chapter 2 - Civil Engineering Applications of Ground Penetrating Radar, Springer Transactions in Civil and Environmental Engineering Book Series, 41–67, 2015.
33. R. Roberts, I. Al-Qadi, E. Tutumluer, J. Boyle, and T.R. Sussmann, Advances in Railroad Ballast Evaluation Using 2 GHz Horn Antennas, in Proc. 11th International Conference on Ground Penetrating Radar, Columbus, OH., USA, 2006.
34. ASTM D6087-08, “Standard Test Method for Evaluating Asphalt-Covered Concrete Bridge Decks Using Ground Penetrating Radar,” ASTM International, West Conshohocken, PA, 2008.
35. J.S. Mundrey, Railway track engineering, Tata McGraw-Hill Education Ed., 2009.
36. F. Benedetto, F. Tosti, A signal processing methodology for assessing the performance of ASTM standard test methods for GPR systems, Signal Processing, 132 (2017) 327–337.
37. EN 13286-2:2005, “Unbound and hydraulically bound mixtures - Part 2: Test methods for the determination of the laboratory reference density and water content - Proctor compaction. European Committee for Standardization, 2015.
38. R.Wu, J. Li, Z.S. Liu, Super resolution time delay estimation via MODEWRELAX. IEEE Aero. Elec. Sys. 35 (1) (1999) 294–307.
39. J. Redman, J. Davis, L. Galagedara, G. Parkin, Field studies of GPR air launched surface reflectivity measurements of soil water content, in Proc. of the 9th International Conference on Ground Penetrating Radar (GPR 2002), Santa Barbara, California, USA, 2002, art. no. 4758, pp. 156-161.
40. J.R. Birchak, C.G. Gardner, J.E. Hipp, J.M. Victor, High dielectric constant microwave probes for sensing soil moisture. Proceedings of the IEEE 62, (1974) 93–102.
41. K., Lichtenecker, K. Rother,: Die herleitung des logarithmischen mischungsgesetzes aus allgemeinen prinzipien der stätionaren strömung. Phys. Z. (1931) 32 255–260.
42. K. Roth, R. Schulin, H. Fluhler, W. Attinger, Calibration of time domain reflectometry for water content measurement using composite dielectric approach, Water Resour. Res. 26 (1990) 2267–2273
43. A. Brovelli, G. Cassiani, Effective permittivity of porous media: a critical analysis of the complex refractive index model, Geophys. Prospect. 56 (2008) 715–727.
44. C. Patriarca, F. Tosti, C. Velds, A. Benedetto, S. Lambot, E.C. Slob, Frequency dependent electric properties of homogeneous multi-phase lossy media in the ground-penetrating radar frequency range, J. Appl. Geophys. 1(97) (2013) 81–88.
45. W. E. Fensler, E. F. Knott, A. Olte, K. M. Siegel, The electromagnetic parameters of selected terrestrial and extraterrestrial rocks and glasses, The moon, (Kopal, Z., and Mikhailov, Z.K., Ed) IAU Symposium 14, 545-565.
46. M.C. Forde, R. De Bold, G. O’Connor, J.P. Morrissey, New analysis of Ground Penetrating Radar testing of a mixed railway trackbed, Transportation Research Board Annual Meeting, 2010.
47. A. Benedetto, A. Umiliaco, Evaluation of hydraulic permeability of open-graded asphalt mixes using a full numerical simulation, J. Mater. Civil Eng. 26 (4) (2014) 599-606.
48. K.S. Kunz, R.J. Luebbers, The Finite Difference Time Domain Method for Electromagnetics”, CRC Press, 1993.
49. A. Taflove, Computational Electrodynamics: The Finite-Difference Time-Domain Method, Artech House, 1995.
50. K.S. Yee, Numerical solution of initial boundary value problems involving Maxwell’s equations in isotropic media, IEEE T. Antenn. P. 14 (1966) 302-307.
51. A. Giannopoulos, Modelling ground penetrating radar by GprMax, Constr. Build. Mater. 19 (10) (2005) 755-762.
52. A. Benedetto, F. Tosti, L. Bianchini Ciampoli, L. Pajewski, D. Pirrone, A. Umiliaco, M.G. Brancadoro, A simulation-based approach for railway applications using GPR, in Proceedings of the 2016 International Conference of Ground Penetrating Radar, Hong Kong, 13-16 June, 2016.