As an expert in the field of information science and bibliometrics, it's my pleasure to explain the concept of a Citation Index to you.
A citation index is a specialized type of bibliographic index that provides a means to retrieve articles or documents based on the references they contain. It is a powerful tool for researchers and academics as it allows them to trace the influence of a particular work or to identify the most influential works in a field. The index lists references in the order of the citing authors, thereby creating a network of citations that can be followed to understand the interconnections between different pieces of literature.
The concept of citation indexing is not new. It has its roots in the early scholarly practices where scholars would acknowledge the works that influenced their research. However, the systematic organization of these citations into an index is a more modern development. The first known form of a citation index can be traced back to the 12th-century Hebrew religious literature, as you mentioned. This early form was rudimentary and served a different purpose than the citation indexes we use today, but it laid the groundwork for the idea of tracking citations.
In the modern context, citation indexes have evolved significantly. They are now an integral part of academic databases and are used for various purposes such as:

1. Bibliographic Verification: To verify the authenticity and credibility of a source by checking its citations.

2. Research Impact Analysis: To measure the impact of a researcher's work by counting the number of citations their work has received.

3. Literature Review: To conduct a comprehensive review of the literature by identifying all the works that cite a particular source.

4. Trend Identification: To identify emerging trends and areas of active research by analyzing citation patterns.

5. Network Analysis: To study the relationships between authors, institutions, and countries by examining the citation network.
One of the most well-known citation indexes is the Science Citation Index (SCI), which was founded by Eugene Garfield in 1963. It covers thousands of journals across a wide range of scientific disciplines. Another notable index is the Social Sciences Citation Index (SSCI), which focuses on the social sciences. These indexes are now part of the Web of Science, a large and comprehensive database that provides access to these citation indexes along with other research tools.
The Scopus database is another significant player in the field of citation indexing. It offers a large abstract and citation database of peer-reviewed literature and quality web sources with smart tools to track, analyze, and visualize research.
Citation indexes are not without their limitations. They can be biased towards certain fields, languages, or regions, and they may not capture all citations, especially those in non-indexed or less formal publications. However, despite these limitations, they remain a valuable resource for researchers and academics.
In conclusion, a citation index is a crucial tool for understanding the academic landscape. It allows researchers to see how their work is being received and to identify the most influential works in their field. As the academic community continues to grow and evolve, so too will the citation indexes that serve it.

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A citation index is a kind of bibliographic index, an index of citations between publications, allowing the user to easily establish which later documents cite which earlier documents. A form of citation index is first found in 12th-century Hebrew religious literature.read more >>