James F. Allen, ``Maintaining knowledge about temporal intervals'', Communications of the ACM, 1983, Vol. 26, No. 11, pp. 832--843; reprinted in: Peter G. Raeth, Expert Systems: A software methodology for modern applications, IEEE Computer Society Press, Los Alamitos, CA, 1990, pp. 248--259.
A pioneer paper of Allen, in which he introduces different ordering relations between intervals and explains how they can be used to represent and process expert knowledge about the times of different events.