Nainggolan, Devi Julietta, et al. “Money Back Warranty on Pricing in Dual Channel Supply Chain (Case Study : Garlick Store Surabaya)”. International Journal of Innovation in Enterprise System, vol. 2, no. 1, Jan. 2018, pp. 19-25, https://ijies.telkomuniversity.ac.id/index.php/IJIES/article/view/13.