The Church feeling of "forbidden textbooks" is from index librorum prohibitorum, initially posted 1564 by authority of Pius IV. The Index Expurgatorius was the catalogue of books that Catholics have been forbidden to read unless particular passages were being deleted, to start with printed 1571. Indexing idea proposed by Robert https://jasperhbtlc.blogdemls.com/5798014/5-tips-about-super-das-you-can-use-today