What this page is
A small collection of org-mode reference files I keep for myself and share with anyone who wants them. Each file is plain text — open it in Emacs for org-mode folding and tags, or in any text editor for raw reading. Free to download, free to modify, free to redistribute.
If you don't use Emacs: the format is just headings (*, **, ***), inline tags (:tag: at the end of a heading), and prose. Plain-text grep-friendly. Nothing in these files requires Emacs to read — Emacs just makes them more pleasant to navigate.
Files
Mathematical Reference
Download math-reference.org · ~60 KB · Released 2026-04-01
A working reference for math formulas and back-of-envelope estimations. Elementary functions, limits, calculus identities, special functions, linear algebra, probability, complex analysis. Tagged against DLMF (Digital Library of Mathematical Functions) and Abramowitz & Stegun section numbers, so you can find the canonical reference for any formula in seconds.
Use I-search in Emacs, or plain rg from the shell. The point is fast lookup when you need a formula, not pedagogy.
Feynman's Playbook — what to do when you're stuck
Download Feynman-math.org · ~30 KB · Released 2026-04-02
A Feynman-style cheatsheet for the moment when an integral, sum, recurrence, or differential equation has stopped you cold. Differentiating under the integral sign, contour deformation, generating functions, the polar trick, dimensional analysis — the moves that turn an impossible problem into a tractable one. With worked examples for each.
License and use
Take them. Edit them. Add to them. Strip headings you don't need. Tag your way into them. If you publish a derivative I'll be glad to link to it from here — drop me an email.