1. First order error propagation in a stagewise smoothing procedure for satellite observations;Swerling;J. Astronaut. Sci.,1959
2. Bryon, A. E., and Frazier, M. Private communication.
3. Smoothing for linear and nonlinear dynamic systems;Bryon,1962
4. New methods and results in linear filtering and prediction theory;Kalman,1962
5. Introduction to Matrix Analysis;Bellman,1960