Paper 1: "Secular Evolution of Spiral Galaxies. I. A Collective Dissipation Process," by Xiaolei Zhang, Astrophysical Journal, 457, 125, 1996

Paper 2: "Secular Evolution of Spiral Galaxies. II. Formation of Quasi-Stationary Modes," by Xiaolei Zhang, Astrophysical Journal, 499, 93, 1998

Paper 3: "Secular Evolution of Spiral Galaxies. III. The Hubble Sequence as a Temporal Evolution Sequence," by Xiaolei Zhang, Astrophysical Journal, 518, 613, 1999