@article{libanio_2005,  title={Unit roots in macroeconomic time series: theory, implications, and evidence},  volume={15},  ISSN={0103-6351},  url={https://doi.org/10.1590/S0103-63512005000300006},  DOI={10.1590/S0103-63512005000300006},  number={3},  journal={Nova Economia},  publisher={Nova Economia},  author={Libanio, Gilberto A.},  year={2005},  month={Sep},  pages={145–176} }