Intro to operators, probabilities, and linear model -- Lp-approximable sequences of vectors -- Convergence of linear and quadratic forms -- Regressions with slowly varying regressors -- Spatial models -- Convergence almost everywhere -- Nonlinear models -- Tools for vector autoregressions

In this paper, we propose Phillips-Perron type, semiparametric testing procedures to distinguish a unit root process from a mean-reverting exponential smooth transition autoregressive one. The limiting nonstandard distributions are derived under very general conditions and simulation evidence...