Table 2. Characteristics of the cluster solutions for the nine similarity approaches.

Approach	# Articles covered	% Coverage	# Clusters	Max Cluster Size
tf-idf MeSH	2,062,642	95.77%	24,708	1517
LSA MeSH	2,115,440	98.22%	25,287	1021
BM25 MeSH	2,011,339	93.39%	26,864	1015
SOM MeSH	2,153,169	99.97%	29,941	3576
tf-idf TA	1,796,349	83.41%	21,388	657
LSA TA	1,958,125	90.92%	23,831	1827
BM25 TA	2,022,694	93.91%	28,858	764
Topics TA	2,033,221	94.40%	24,163	1422
PMRA	2,029,564	94.23%	28,963	921