The author holds an NSERC University Faculty Award and is
supported by a Discovery Grant. She thanks Michael Kramer, George
Hobbs, and Zaven Arzoumanian for careful readings of the
manuscript, Duncan Lorimer for generously sharing his keyworded
reference list, and Gilles Esposito-Farèse, Michael Kramer, Joe
Taylor, Steve Thorsett, Willem van Straten, and Joel Weisberg for
allowing reproduction of figures from their work. The Arecibo
Observatory, a facility of the National Astronomy and Ionosphere
Center, is operated by Cornell University under a cooperative
agreement with the National Science Foundation. The National
Radio Astronomy Observatory is a facility of the National Science
Foundation operated under cooperative agreement by Associated
Universities, Inc. The Parkes radio telescope is part of the
Australia Telescope which is funded by the Commonwealth of
Australia for operation as a National Facility managed by CSIRO.