Barsky, Robert B. and Jeffrey A. Miron (1989) The Seasonal Cycle and the Business Cycle. Journal of Political Economy, 97 (3): 503-32.
Granger, Clive William John and Newbold, Paul (1986) Forecasting Economic Time Series. 2nd edition. Published by New Milford, Connecticut, U.S.A.: Emerald Group Pub Ltd.
Javier Lopez-de-Lacalle in https://github.com/cran/uroot/blob/master/R/hegy.R