1. Bryan, Martin.SGML: An Author's Guide to the Standard Generalized Markup Language. Addison-Wesley, 1988. [Detailed text book giving full treatment of the standard, but primarily from the publishing perspective.]
2. Coombs, James H.,et al. “Markup Systems and the Future of Scholarly Text Processing”.Communications of the ACM, 30, 11 (1987), 933–47. [Classic polemic in favour of descriptive over procedural markup presented from the scholarly perspective.]
3. DeRose, Steven J.,et al. “What is Text, Really?”Journal of Computing in Higher Education, 1, 2 (1990).
4. Goldfarb, Charles.The SGML Handbook. Oxford University Press, 1991. [Authoritative and exhaustive presentation of all aspects of ISO 8879, including annotated and cross referenced full text of the standard itself.]
5. International Organization for Standardization. “ISO 8879: Information Processing — Text and Office Systems — Standard Generalized Markup Language (SGML) (ISO, 1986)”. [Annexes A and B to the Standard provide a formal but readable summary of its most important features.]