Roget's Thesaurus of Words for Writers: Over 2,300 Emotive, Evocative, Descriptive Synonyms, Antonyms, and Related Terms Every Writer Should Know by David Olsen, Michelle Bevilacqua, Justin Cord Hayes, Robert W Bly, Paperback
More 1100 Gap Synonyms. Similar words for Gap.
Historical Thesaurus :: About the Thesaurus
2 Principal Science and Technology Gaps | Advice on the Department of Energy's Cleanup Technology Roadmap: Gaps and Bridges | The National Academies Press
A thesaurus for phytoplankton trait-based approaches: Development and applicability - ScienceDirect