1. An extrapolator and scrutator;Duffin;J. Math. Anal. Appl.,1960
2. An exponomial extrapolator;Duffin;J. Math. Anal. Appl.,1961
3. Extrapolating time series by discounted least squares;Duffin;J. Math. Anal. Appl.,1967
4. Smoothing, Forecasting and Prediction of Discrete Time Series;Brown,1963
5. Introduction to Sequential Smoothing and Prediction;Morrison,1969