Sarkum, Sumitro, Bambang Agus Pramuka, and Agus Suroso. 2017. “A Strategy Engagement in Marketing: A Reviews of the Literature”. International Journal of Sciences: Basic and Applied Research (IJSBAR) 33 (2):120-27. https://www.gssrr.org/index.php/JournalOfBasicAndApplied/article/view/6899.