@article{o'donnell_2007,  title={Access to health care in developing countries: breaking down demand side barriers},  volume={23},  ISSN={0102-311X},  url={https://doi.org/10.1590/S0102-311X2007001200003},  DOI={10.1590/S0102-311X2007001200003},  number={12},  journal={Cadernos de Saúde Pública},  publisher={Escola Nacional de Saúde Pública Sergio Arouca, Fundação Oswaldo Cruz},  author={O'Donnell, Owen},  year={2007},  month={Dec},  pages={2820–2834} }