Algorithms for Finding the Axis of a Helix: Fast Rotational and Parametric Least-squares Methods. - Jon A. Christopher; Rosemarie Swanson; Thomas O. Baldwin (Comput. Chem., 1996)

TEXTAL: A Pattern Recognition System for Interpreting Electron Density Maps. - Thomas R. Ioerger; Thomas Holton; Jon A. Christopher; James C. Sacchettini (ISMB, 1999)