ACM SIGMOD Anthology, Volume 4, Issue 1:
Selected Material from the Symposium on Principles of Programming Languages (POPL)

POPL 1982

• Eric C. Cooper:
  On the Expressive Power of Query Languages for Relational Databases. 361-365
  

POPL 1981

• Ashok K. Chandra:
  Programming Primitives for Database Languages. 50-62
  

POPL 1979

• Marco A. Casanova, Philip A. Bernstein:
  The Logic of a Relational Data Manipulation Language. 101-109
  
• Alfred V. Aho, Jeffrey D. Ullman:
  The Universality of Data Retrieval Languages. 110-120