Twardy, Juliusz. “Evolution of Periglacial Dells and Valleys During the Holocene in the Vicinity of Łódź: Https: doi.Org 10.26485 AGL 2017 106 2”. Acta Geographica Lodziensia, vol. 106, Dec. 2018, pp. 17-30, https://czasopisma.ltn.lodz.pl/Acta-Geographica-Lodziensia/article/view/73.