BibTex format
@article{Ahmed:2007:10.1107/S0907444907029976,
author = {Ahmed, HU and Blakeley, MP and Cianci, M and Cruickshank, DWJ and Hubbard, JA and Helliwell, JR},
doi = {10.1107/S0907444907029976},
journal = {Acta Crystallographica Section D},
pages = {906--922},
title = {The determination of protonation states in proteins},
url = {http://dx.doi.org/10.1107/S0907444907029976},
volume = {63},
year = {2007}
}