Improved inclusion-exclusion identities via closure operators Klaus Dohmen Department of Computer Science, Humboldt-University Berlin, Unter den Linden 6, D-10099 Berlin, Germany E-mail: [email protected] received March 24, 1999, revised September 6, 1999, accepted April 15, 2000. Let be a finite family of sets. We establish an improved inclusion-exclusion identity for each closure...