“…The user-produced contents carry useful information about the articles' contents and users' attitudes (Yin et al, 2016). As the citation contexts revealed to be effective in scientific information retrieval (Eto, 2013), it seems rational to seek for improving the retrieval of scientific documents by the application of comments and recommendations, especially those posted by experts and peer reviews, because they are rich sources of information and appropriately represent the contents of the related articles (Rashidi et al, 2020;Koolen, 2014;Yin et al, 2016;Wang et al, 2012;Potthast et al, 2012;Cunningham and Nichols, 2008;Yamamoto et al, 2008;Yee et al, 2009;Hu et al, 2008). Given the differences of individuals in their knowledge horizons, any user may have her own perception of the document she reads and use different terms when commenting on it (Bouadjenek et al, 2016), and thereby bring about diversity in the wordings and terminologies.…”