@article{Im2003,
author = {Im, K.S. and Pesaran, M.H. and Shin, Y.},
title= {Testing for unit roots in heterogeneous panels},
year = {2003},
doi = {10.1016/S0304-4076(03)00092-7},
journal = {Journal of Econometrics},
volume = {115},
number = {1},
pages = {53--74},
}