1. R. E. Kalman, “A new approach to linear filtering and prediction problems,” J. Basic Eng. ASME, 82, 1960, pp. 33–45.
2. R. E. Kalman and R. S. Bucy, “New results in linear filtering and prediction theory,” J. Basic Engr. ASME Series D, 83, 1961, pp. 95–108.
3. R. S. Bucy, “Nonlinear filtering,” IEEE Trans. Automatic Control, AC-10, 1965, p. 198.
4. H. J. Kushner, “On the differential equations satisfied by conditional probability densities of Markov processes,” SIAM J. Control, 2, 1964, pp. 106–119.
5. A. N. Shiryaev, “Some new results in the theory of controlled stochastic processes [Russian],” Trans. 4th Prague Conference on Information Theory, Czech. Academy of Sciences, Prague, 1967.