手法を比較

	グレィ・リテラチャー・サーチ（非商業的文献検索）	ブール演算子	引用分析
分野	研究スキル	研究スキル	研究スキル
系統	Process / pipeline	Process / pipeline	Process / pipeline
提唱年	1990s (formalized in systematic review guidelines)	1847 (Boolean algebra); 1960s (database applications)	1955 (citation indexes); 1975 (Impact Factor); 2005 (H-index)
提唱者	Information specialists and systematic review methodologists (Cochrane Collaboration, Health Technology Assessment)	George Boole and IT information retrieval practitioners	Eugene Garfield (Citation Indexes, 1955); Jorge Hirsch (H-index, 2005)
種類	Tool	Tool	Tool
原典	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.	Wilkinson, M. D., Sansone, S. A., Vandervalk, B., & Rocca-Serra, P. (2011). Evaluating information retrieval systems: a guide for researchers. Expert Review of Molecular Diagnostics, 11(2), 181–190.	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.
別名	grey literature, gray literature, unpublished literature	Boolean logic, Boolean search, AND OR NOT	citation metrics, bibliometric analysis, citation tracking
関連	3	2	4
概要	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.	Boolean search operators are logical functions—AND, OR, NOT, and parentheses—used to combine and filter search terms in bibliographic databases, library catalogs, and search engines. Named after mathematician George Boole (1815–1864), Boolean logic has been applied to information retrieval since the 1960s. These operators allow researchers to construct complex, precise searches that retrieve only articles meeting specific combinations of criteria, dramatically improving search efficiency and reducing irrelevant results.	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.