1. Marston A (1922) Second progress report to the Joint Concrete Culvert Pipe Committee. Iowa Engineering Experimental Station, Ames, IA, USA
2. Marston A (1930) The theory of external loads on closed conduits in the light of the latest experiments. In: The 9th annual meeting of the highway research board. Highway Research Board, Washington, D.C., USA, pp 138–170
3. Spangler MG (1950) Field measurements of the settlement ratios of various highway culverts, Bulletin No. 170. Iowa Engineering Experiment Station, Ames, Iowa, USA, p 99
4. Spangler MG (1951) A theory on loads on negative projecting conduits. In: The 13th annual meeting of the highway research board. Washington, D.C., USA, pp 153–161
5. Sladen JA, Oswell JM (1988) The induced trench method—a critical review and case history. Can Geotech J 25(3):541–549