Refunds

If the book is not what you expected, write to inshihub.com@gmail.com within 14 days of purchase from the email address used at checkout, and we will refund the order in full. You do not need to give a reason, though feedback helps us improve the material.

If you find a mathematical error, report it any time: confirmed errors are corrected in a versioned update that every buyer can re-download free. The reporting steps and current release versions are listed in the corrections and release history.