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Understanding the codes

This site follows the MSC2020 Mathematics Subject Classification, the scheme used by Mathematical Reviews and zbMATH to classify research. Codes get more specific as they get longer:

• 05 is a topic — a broad area, e.g. Combinatorics.
• 05Cxx is a subtopic within it, e.g. Graph theory.
• 05C05 is a specific topic, e.g. Trees.

The five Roman-numeral branches (I–V) in the navigation bar are broad groupings of related topics, to make browsing more manageable than a flat list of ~60 topics.

Finding a topic

• Search (on the home page and every topic/subtopic page) matches on code, title, or a keyword from the description — try a code fragment like 05C, a name like "graph theory," or a keyword like "network."
• Browse from the home page: pick a branch, then a topic, then a subtopic, then a specific topic.
• Mind map: an interactive visual layout of the whole hierarchy — hover a topic to see its subtopics, click any node to jump to its page.

What's on a specific-topic page

Each specific topic (e.g. 05C05 Trees) covers: an overview, a link to the relevant Wikipedia article, useful external links, key ideas, typical uses, applications, references, and recommended textbooks.

• References are academic papers — journal articles, arXiv preprints — not books, and each is individually checked against a real source (not just an automated guess) before being added. A "Google Scholar (PDF results)" link accompanies each one to help you find a downloadable copy.
• Recommended Textbooks are books, each with an Amazon link.

Open Textbooks & Gutenberg Library

Alongside the MSC hierarchy, two pages collect free-to-read books by topic:

• Open Textbooks — modern courses released under an open license (GFDL, CC BY, etc.) by their authors or publishers.
• Gutenberg Library — public-domain mathematics texts and classics from Project Gutenberg, categorized by subject.

Both link out to the original source rather than hosting copies.

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