@article{Blakely2000,
author = {Blakely, T.A. and Woodward, A.J.},
title= {Ecological effects in multi-level studies},
year = {2000},
doi = {10.1136/jech.54.5.367},
journal = {Journal of Epidemiology and Community Health},
volume = {54},
number = {5},
pages = {367--374},
}