Researcher Institute of Mathematics, Bulgarian Academy of Sciences, Sofia, 1978-1980, 84-85, senior researcher, 1986-1991. Lecturer University l'Aquila, Italy, 1991-1992. Professor Udine (Italy) University, since 1992.
Visiting professor University Padua, Italy, 1982-1983, 91-92, Aquila University, 1989, York University, Toronto, Ontario, Canada, 1989, 91, 93, 2003, 2005, University Berne, 1994, University Matsuyama, Japan, 1994, 98, 2002-2003, City University of New York, 1995, Wesleyan University, 1995, West Virginia University, 1995-1996, 99, California State University, 1996, Universidad Autónoma Metropolitana Mexico, 1997, 99, 2004, Tulane University 1997, Ljubljana University, 1997-2000, Southern Mississippi University, 1997, University Jaume I., Castello, Spain, 2000, 2003, 05, University Western Australia, Perth, 2000, University South Australia, Adelaide, 2000, Miami University, 2002, Bar Ilan University, Tel Aviv, 2004, Wisconsin University, Madison, 2004, Coimbia University, Portugal, 2005, Comlutense University, Madrid, 2005, Technology University, Wien, 2005, Vrije University, Brussels, 2007.
- Categorical Structure of Closure Operators: With Applications to Topology, Algebra and Discrete Mathematics (Mathematics and Its Applications)
- Our motivation for gathering the material for this book over aperiod of seven years has been to unify and simplify ideas wh ich appeared in a sizable number of re search articles during the past two decades.
- Topological Groups: Characters, Dualities, and Minimal Group Topoligies (Pure and Applied Mathematics) (Vol 130)
- Topological groups: Characters, dualities, and minimal group topologies (Monographs and textbooks in pure and applied mathematics)