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
分野	研究スキル	研究スキル
系統	Process / pipeline	Process / pipeline
提唱年	1990s (formalized in systematic review guidelines)	1847 (Boolean algebra); 1960s (database applications)
提唱者	Information specialists and systematic review methodologists (Cochrane Collaboration, Health Technology Assessment)	George Boole and IT information retrieval practitioners
種類	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.
別名	grey literature, gray literature, unpublished literature	Boolean logic, Boolean search, AND OR NOT
関連	3	2
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.