Much of my work has involved collaboration with a number of experimental groups around the world. The degree of such collaboration has ranged from brief interaction on a particular problem to ongoing joint projects resulting in a number of joint papers. Examples of laboratories involved or having been involved in such collaboration are: Saclay, France; University of Bielefeld; Max Planck Institute for Quantum Optics, Munich; University of Aarhus, Denmark; University of Crete, Greece; Australian National University, Canberra; JILA, University of Colorado; Oak Ridge National Laboratory USA; Brookhaven National Laboratory USA; National Institute of Standards and Technology USA; Livermore National Laboratory USA.