interval.sourceforge.net/interval/refs.html

• "Interval Arithmetic: from Principles to Implementation" (.ps.gz 96K)
  JACM Vol. 48, number 5, pages 1038-1068, September 2001
  by Timothy J. Hickey, Qun Ju, and Maarten H. van Emden
  Tech. Rep. CS-99-202, CS Dept. Brandeis U, July 1999.

• "A Unified Framework for Interval Constraints and Interval Arithmetic",
  by Timothy J. Hickey, Maarten H. van Emden, and Huan Wu,
  in Principles and Practice of Constraint Programming -- CP98
  Michael Maher and Jean-Francois Puget (eds.), Springer-Verlag,
  Lecture Notes in Computer Science, v. 1520, pp. 250-264, 1998.