@ARTICLE {4467,
author={J. J. O.  Pires and L.   Cancela},
doi={10.1109/LCOMM.2009.09010922},
journal={IEEE Communications Letters},
title={Simplifying the Error Probability Analysis in Optical Direct Detection DPSK Systems},
year={2009},
month={June},
volume={13},
number={6},
pages={369-371},
ISSN={1089-7798}
}