Qian, Zhi-Wang, et al. „Performance Evaluation of Digital Marketing in Health Care Industry with the Application of Data Envelopment Analysis”. Revista de Cercetare si Interventie Sociala, vol. 60, martie 2018, pp. 39-50, https://www.rcis.ro/journal/article/view/2417-performance-evaluation-of-digital-marketing-in-health-care.