So sánh phương pháp

	Phân tích trích dẫn	Tìm kiếm tài liệu xám
Lĩnh vực	Kỹ năng nghiên cứu	Kỹ năng nghiên cứu
Họ	Process / pipeline	Process / pipeline
Năm ra đời	1955 (citation indexes); 1975 (Impact Factor); 2005 (H-index)	1990s (formalized in systematic review guidelines)
Người khởi xướng	Eugene Garfield (Citation Indexes, 1955); Jorge Hirsch (H-index, 2005)	Information specialists and systematic review methodologists (Cochrane Collaboration, Health Technology Assessment)
Loại	Tool	Tool
Công trình gốc	Hirsch, J. E. (2005). An index to quantify an individual's scientific research output. Proceedings of the National Academy of Sciences, 102(46), 16569–16572.	Rothstein, H. R., & Hopewell, S. (2009). Grey literature. In J. P. Higgins & S. Green (Eds.), Cochrane handbook for systematic reviews of interventions (Version 5.0.2, Chapter 13). The Cochrane Collaboration.
Tên gọi khác	citation metrics, bibliometric analysis, citation tracking	grey literature, gray literature, unpublished literature
Liên quan	4	3
Tóm tắt	Citation analysis is the systematic study of how scholarly works are cited by subsequent research, used as a proxy for research impact and influence. Founded formally by Eugene Garfield in 1955 (introducing citation indexes), the field encompasses metrics ranging from simple citation counts to sophisticated indices like the H-index (Hirsch, 2005) and field-normalized indicators. Citation analysis is used to evaluate researcher productivity, track influence of ideas, assess journal quality, and detect research trends. While citation counts are not perfect measures of quality (high citation does not equal high quality; time lag in citation accumulation), they provide valuable quantitative data for research evaluation alongside peer review and expert assessment.	Grey literature comprises documents and data not published through conventional commercial channels—including theses, government reports, clinical trial registries, conference abstracts, organizational policy documents, and working papers. Unlike journal articles, grey literature is not indexed in MEDLINE or Scopus and often lacks peer review. However, it is crucial for systematic reviews because it may contain null or negative findings that are less likely to be published (publication bias). Systematic grey literature searching is now a standard component of evidence synthesis and is recommended by the Cochrane Collaboration, PRISMA, and other methodological guidelines.