Terms of sale

EngineerProof sells digital study materials delivered as PDF downloads. Payment is processed by Stripe; we never see or store card details.

License

Each purchase grants the buyer a personal, non-transferable license to download, print, and study from the purchased edition. The delivered file is stamped with the order reference. Redistribution, resale, public upload, or removal of the delivery mark is not permitted. Mandatory rights under applicable law are unaffected.

Delivery and re-download

The download link on the confirmation page is also sent in a separate EngineerProof delivery email. It remains valid for 90 days and always serves the newest corrected edition. After expiry, write to inshihub.com@gmail.com from the purchase email address for a fresh link.

Accuracy

Solutions are verified by two independent calculation routes before publication. Corrections are published with version numbers. The materials are study aids; no passing outcome is promised or implied.

Seller disclosure

Seller identity, contact, pricing, payment, and delivery information required under Japan's Act on Specified Commercial Transactions is listed in the commercial disclosure.