Gradkowski, Krzysztof. “Flexibility of Layers of Model Subbase of Pavement and Strengthening Effect With Geotexstile”. Roads and Bridges – Drogi I Mosty, vol. 6, no. 2, Apr. 2007, pp. 5-16, https://www.rabdim.pl/index.php/rb/article/view/v6n2p5.