​(2024-Present). Editor, zbMATH Open, Department of Mathematics, FIZ Karlsruhe – Leibniz Institute for Information Infrastructure, Germany, European Mathematical Society.

(2019-Present) Mathematical Scientist and Educator, Ann Arbor, MI, USA.

(2020-2021). Visiting Scholar, University of Michigan, Ann Arbor, Michigan, USA.

(2013-2019). Associate Editor, Mathematical Reviews, American Mathematical Society.

(2005-2006). New Directions Professor, Institute for Mathematics and its Applications (IMA), University of Minnesota, USA.
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(2013-2019) Associate Editor, Mathematical Reviews, American Mathematical Society. and Sponsored affiliate, Department of Mathematics, University of Michigan.

(2000-2012) Full, Associate and Assistant Professor, Department of Mathematics, Georgia Southern University.

(2007-2013) Founder and Director of the Unit for Advances in Mathematics (IUAM). (IUAM is an interdisciplinary university institute with home the College of Science and Mathematics).

(2005-2006) New Directions Research Professor, Institute of Mathematics and its Applications (IMA), University of Minnesota. [on leave].

(2008-2011) Visiting Full Professor, School of Computational and Applied Mathematics, University of the Witwatersrand. [Joint appointment with GSU].

(Fall 2007) Visiting Professor, Department of Mathematics, University of the Witwatersrand. [On leave].

(1999-2000) Visiting Professor, Department of Mathematics, Pennsylvania State University [On leave].

(1998-2000) Research Associate of the John Knopmacher Centre for Applicable Analysis and Number Theory and Lecturer, Department of Mathematics, the University of the Witwatersrand.

(1996-1997) Postdoc, Department of Mathematics, University of South Florida and Visitor, Katholieke Universiteit, Leuven.​