The bibtex entries that you download from researchr may contain non-ASCII characters, such as with the authors of the following paper:
@article{SchurrD05,
title = {Introductory paper},
author = {Andy Schürr and Heiko Dörr},
year = {2005},
doi = {http://dx.doi.org/10.1007/s10270-004-0069-7},
journal = {Software and Systems Modeling},
volume = {4},
number = {2},
pages = {109-111},
}
To use such entries in your LaTeX document, use the inputenc.sty package as follows:
\usepackage[utf8]{inputenc}