E. E. Pangaribuan, H. Sabrina, and A. M. U. Nasution, “The Effect of Free Shipping and Timeliness of Product Delivery on Purchasing Decisions on the Shopee Application at Kec.Borbor Kab.Toba”, SAJMR, vol. 3, no. 2, pp. 115–130, Feb. 2025.