The now missing Google Books on iOS

Update: Amazon’s Kindle and Barnes and Noble’s Nook both killed their store links as well.

The WSJ is reporting that Apple is laying down the law on apps that try to link externally to other payment systems in the App Store.  The WSJ’s own app and Kobo, another eBookseller were both forced to remove external links to payment stems from within their apps.

In a pair of moves that suggest Apple Inc. is enforcing rules for selling content on its devices, Kobo Inc., the Canadian e-book retailer, and The Wall Street Journal said Sunday they will no longer sell content directly to customers through their apps for Apple devices.

We reported last week and over the weekend that Google Books was pulled from the App Store without a trace. Google and Apple (shocker) will not give us comment on the matter.  Now the Journal chimes in:

Google Inc., which competes with Apple to sell e-books and other content, also appeared to have been affected. Google Books, a mobile app that lets people buy e-books, among other things, wasn’t available in the iTunes app store as of Sunday night. A Google spokesman declined to comment.