How Can SMEs Become More Sustainable? Modelling the M-Commerce Consumer Behaviour with Contingent Free Shipping and Customer Journey’s Touchpoints Optimisation - Nichifor, Eliza; Lixăndroiu, Radu Constantin; Sumedrea, Silvia; Chițu, Ioana Bianca; Brătucu, Gabriel (MDPI AG, 2021)