@article{ref1,
title="Events per person year. Use individual event rate adjustment for follow up time",
journal="British medical journal: BMJ",
year="1995",
author="Löyttyniemi, E. and Laitinen, K. and Tuominen, J.",
volume="310",
number="6992",
pages="1469-1470",
abstract="<p>[Abstract unavailable]</p><p>Language: en</p>",
language="en",
issn="0959-8138",
doi="",
url="http://dx.doi.org/"
}