[1]
T. M. Connolly and C. E. Beg, Database systems: a practical approach to design, implementation, and management, Sixth edition. Harlow, Essex, England: Pearson, 2015 [Online]. Available: https://ebookcentral.proquest.com/lib/uea/detail.action?docID=5136720
[2]
R. F. van der Lans, Introduction to SQL: mastering the relational database language, 4th ed. Upper Saddle River, N.J.: Addison-Wesley, 2006 [Online]. Available: https://www.oreilly.com/library/view/introduction-to-sql/0321305965/?ar