CHUKWU, Godswill Chinedu; DAGOGO, Domo. Free sample usage and sales performance of selected supermarkets in port harcourt metropolis. International Journal on Integrated Education, [S. l.], v. 4, n. 5, p. 148–165, 2021. DOI: 10.31149/ijie.v4i5.1797. Disponível em: https://journals.researchparks.org/index.php/IJIE/article/view/1797. Acesso em: 5 nov. 2026.