Valuev Circular
The Valuev Circular of 18 July 1863 was a decree issued by Pyotr Valuev, List of [Ministers of Interior of Imperial Russia|Minister of Internal Affairs] of the Russian Empire, by which many publications in the "Little Russian" language were forbidden, except for belles-lettres works.
History
The circular put the reason for the growing number of textbooks in Ukrainian and beginner-level books in Ukrainian as "the Poles' political interests" and the "separatist intentions of some of the Little Russians". The circular quoted the opinion of the Kiev Censorship Committee that "a separate Little Russian language never existed, does not exist, and shall not exist, and the tongue used by commoners is nothing but Russian corrupted by the influence of Poland."The circular ordered the Censorship Committees to ban the publication of religious texts, educational texts, and beginner-level books in Ukrainian; but permitted publication of belles-lettres works in the language.
Further restrictions were placed on Ukrainian by the Ems Ukaz in 1876, which completely prohibited the usage of the language in open print.