While on sabbattical from CUNY, I held a Visiting Professor position at the Universiteit van Amsterdam at the Institute for Logic, Language and Computation during April–August 2007. During the two years previous to this, I was an NWO-sponsored Bezoekersbeurs Visiting Researcher there, during June–August 2005 and June 2006.  While in Amsterdam, I worked with Benedikt Löwe, particularly on our work concerning the modal logic of forcing.