Terms of Use
Last updated: October 23, 2026
By using math4ai.org you agree to these terms. If you don't, please don't use the site.
Membership
- Membership comes with a copy of the book: once we verify your receipt at /redeem/, your account can read the online book and use the Companion, videos and songs.
- It is personal: one person per account. Don't share your login or the materials.
- We may suspend an account that redistributes the materials or abuses the site.
The materials
Everything on the site is protected by copyright (see the copyright notice). Members may use it for their own study. Don't download, copy, record, upload or post the online book, videos or songs, or use them commercially, without written permission.
Upgrading a printed copy
- Readers who bought an earlier copy can order one copy of the current printed edition at cost: the printer's charge for the order (printing, shipping and tax) plus PayPal's fee. We make no profit on it. The page shows the exact price before you pay.
- The book is printed and shipped by Lulu. Delivery times are Lulu's estimates.
- Outside the United States, customs in your country may charge import duties or taxes on delivery; those are yours to pay.
- Problems: if a copy arrives damaged or misprinted, email us with a photo within 30 days and we'll arrange a replacement through Lulu. Because each copy is printed to order, we can't take back books that are fine.
- Changed your mind? Email us within about two hours of paying: until then printing hasn't started and we can cancel the order with a full refund. After that it is being printed and can't be stopped.
Acceptable use
Don't try to break into the site, get around the membership, overload it, upload anything that isn't a genuine receipt, or use it to send spam.
Changes
We may update these terms; the date at the top shows the latest version.
Contact
Questions: xuanxinjushi@gmail.com.