1. Brock, D., Customer relationship marketing, Scribl, 2019.
2. Tripathi, S., CRM in pharmaceutical and healthcare marketing, Clever Fox Pub., 2020.
3. Shanthi, R., Customer relationship management, MJP Publisher, 2019.
4. Horn, B., The customer service revolution, AuthorHouse, 2020.
5. Christopher, M. et al., Relationship marketing: creating sharholder value, Routledge, 2002.