  The results of bibliometric studies provided by bibliometric research groups,
e.g. the Centre for Science and Technology Studies (CWTS) and the Institute for
Research Information and Quality Assurance (iFQ), are often used in the process
of research assessment. Their databases use Web of Science (WoS) citation data,
which they match according to their own matching algorithms - in the case of
CWTS for standard usage in their studies and in the case of iFQ on an
experimental basis. Since the problem of non-matched citations in WoS persists
because of inaccuracies in the references or inaccuracies introduced in the
data extraction process, it is important to ascertain how well these
inaccuracies are rectified in these citation matching algorithms. This paper
evaluates the algorithms of CWTS and iFQ in comparison to WoS in a quantitative
and a qualitative analysis. The analysis builds upon the methodology and the
manually verified corpus of a previous study. The algorithm of CWTS performs
best, closely followed by that of iFQ. The WoS algorithm still performs quite
well (F1 score: 96.41 percent), but shows deficits in matching references
containing inaccuracies. An additional problem is posed by incorrectly provided
cited reference information in source articles by WoS.
