Correspondence: Reply to 'Challenges with dating weathering products to unravel ancient landscapes'. Issue 1 (December 2017) - Fredin, Ola; Viola, Giulio; Zwingmann, Horst; Sørlie, Ronald; Brönner, Marco; Lie, Jan-Erik; Grandal, Else; Müller, Axel; Margreth, Annina; Vogt, Christoph; Knies, Jochen