Robin Hirsch's articles on Intervals.

• R. Hirsch. Relation algebras of intervals.
  My thesis has three sections: Relation Algebra; Intervals; Applications in Planning. Diagrams are missing.
  
• R. Hirsch. From points to intervals
  In the Journal of Applied Non-Classical Logic , volume 4 number 1, pp 7 - 27, 1994. (The postscript version here has diagrams missing)
  
• R. Hirsch. Relation algebras of intervals
  In Artificial Intelligence Journal, vol. 83, pp 1-29, 1996. Diagrams are missing.