In this paper, we analyze the adequacy and applicability of readership statistics recorded in social reference management systems for creating knowledge domain visualizations. First, we investigate the distribution of subject areas in user libraries of educational technology researchers on Mendeley. The results show that around 69 of the publications in an average user library can be attributed to a single subject area. Then, we use co-readership patterns to map the field of educational technology. The resulting visualization prototype, based on the most read publications in this field on Mendeley, reveals 13 topic areas of educational technology research. The visualization is a recent representation of the field: 80 of the publications included were published within ten years of data collection. The characteristics of the readers, however, introduce certain biases to the visualization. Knowledge domain visualizations based on readership statistics are therefore multifaceted and timely, but it is important that the characteristics of the underlying sample are made transparent.
A new form of document coupling called co-citation is defined as the frequency with which two documents are cited together. The co-citation frequency of two scientific papers can be determined by comparing lists of citing documents in the Science Citation Index and counting identical entries. Networks of co-cited papers can be generated for specific scientific specialties, and an example is drawn from the literature of particle physics. Co-citation patterns are found to differ significantly from bibliographic coupling patterns, but to agree generally with patterns of direct citation. Clusters of co-cited papers provide a new way to study the specialty structure of science. They may provide a new approach to indexing and to the creation of SDI profiles. Mendeley's crowd-sourced catalogue of research papers forms the basis of features such as the ability to search for papers, finding papers related to one currently being viewed and personalised recommendations. In order to generate this catalogue it is necessary to deduplicate the records uploaded from users' libraries and imported from external sources such as PubMed and arXiv. This task has been achieved at Mendeley via an automated system. However the quality of the deduplication needs to be improved. "Ground truth" data sets are thus needed for evaluating the system's performance but existing datasets are very small. In this paper, the problem of generating large scale data sets from Mendeley's database is tackled. An approach based purely on random sampling produced very easy data sets so approaches that focus on more difficult examples were explored. We found that selecting duplicates and non duplicates from documents with similar titles produced more challenging datasets. Additionally we established that a Solr-based deduplication system can achieve a similar deduplication quality to the fingerprint-based system currently employed. Finally, we introduce a large scale deduplication ground truth dataset that we hope will be useful to others tackling deduplication.