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nLab is a collaborative, wiki-style reference for higher mathematics, with a focus on category theory, higher algebra, and related fields. It offers extensive, concept-driven articles on cohomology (including group, sheaf, and derived aspects), homotopy theory, stacks, topos theory, and other interconnected topics, along with definitions, explanations, and literature links.
More resources on Cohomology
Hatcher's Algebraic Topology
Free online book covering cohomology comprehensively
Algebraic Topology
Explore cohomology and other key concepts in algebraic topology with this course taught by Joe Harris.
nLab Cohomology
Reference page with AG-specific cohomology
Milne's Etale Cohomology Notes
Free PDF notes, highly recommended on Reddit
Stacks Project
Comprehensive free resource covering sheaf, etale cohomology in AG
Sheaf Cohomology
Learn Sheaf Cohomology with this course from the University of Bonn! Explore advanced cohomology topics.