## 2 Literature Review
The proposed system automatically employs the citation context as a query in local citation recommendations and mines articles' subjects as queries in context-aware recommendation tasks to recommend related reference sources. Scientific impact measurements are traditionally based on the total number of citations. [PERSON] [39] investigated the impact of a researcher by presenting an automated system to count both direct (to include the author's surname as part of the text and year of publication in parentheses) and indirect citations (to include both the author's surname and year of publication in parentheses) of a publication. According to him, to assess a researcher's scientific impact one needs to sum the citations of all articles. Using medical articles from 1991 to 2001 from the WoS database, [PERSON] et al. [40] measured the annual citation count of each publication and concluded that knowledge is rarely consumed in the same year in which it is produced: a publication achieves a representative citation count two years after its publication. Similar results were reported by [PERSON], [PERSON], and [PERSON] [41], who investigated the influence of a highly cited article on those citing articles published between 2006 and 2014 and indexed in the WoS database. They proposed using the citation context with specific features (citation location, citation mention, and citation topic) and observed the change in articles' impact over a nine-year interval after publication. They concluded that the consumption of H-index articles peaked in the first two years, until 2007, and then started declining, with fluctuations. [PERSON] [42] claimed that the concepts or ideas introduced in publications lead to new ideas that will, in turn, be published in articles on similar topics soon. Therefore, citations between publications imply a knowledge flow from the author of the article being cited to the author of the article that cites it. Another approach, by [PERSON] et al. [43], deployed the citation influence model to reveal the production and consumption of knowledge in the field of physics across various countries. They analyzed the studies published in the American Physical Society (APS) over a 50-year time interval (1960-2009). The results concluded that, in the early years, the United States was the top producer of knowledge in the field of physics, whereas in the early 1990s the United Kingdom and northern Europe were the dominant producers. Throughout this time, China was the largest consumer of knowledge worldwide. Many studies have presented novel measures to calculate the spread of scientific knowledge, such as the Rowlands Diffusion Index [44] and the Frandsen Diffusion Index [45]. [PERSON] and [PERSON] [46] proposed a novel metric to measure the citation impact of countries by analyzing Elsevier's Scopus citation database in the subject area of energy for the years 1996 to 2009. The proposed metric is entitled the International Scholarly Impact of Scientific Research (ISISR), and it calculates the number of citations of an article in a particular domain by researchers from both beyond and within the source country. The results indicate that China produced more publications in the field of energy, but that they were not referenced by the international research community, whereas the United States produced fewer publications that are referenced internationally. Researchers have used various publication sets to measure the diffusion of knowledge between several units, such as among subject categories, journals, institutions, scientists, and countries. To investigate the international visibility of journals, [PERSON] and [PERSON] [47] adopted a journal-citation analysis approach. Using two databases, Science Citation Index (SCI) and China Scientific and Technical Papers and Citations Database (CSTPCD), they compared the citation count of Chinese articles to that of international publications.