Pergamentshikov, S., and A. Shiryaev. “On Reparametrization and Asymptotically Optimal Minimax Estimation in a Generalized Autoregressive Model”. Annales Fennici Mathematici, vol. 17, no. 1, Feb. 1992, pp. 111-6, doi:10.5186/aasfm.1992.1714.