Abdullah Uz Tansel Erkan Tin Expressive Power of Temporal Relational Query Languages and Temporal Completeness. 129-149 1997 Temporal Databases, Dagstuhl db/conf/dagstuhl/dagstuhl-tdb97.html#TanselT97 http://link.springer.de/link/service/series/0558/bibs/1399/13990129.htm