excerpt from an online reference: (wikipedia) ".....The importance of the first printed Cyrillic Bible can hardly be overestimated. Prince Ostrogski sent copies to pope gregory xiii and
tsar Ivan the Terrible, while the latter presented a copy to an English ambassador. When leaving Ostroh, Fyodorov took 400 books with him.
Only 300 copies of the Ostrog Bible are extant today.
The
Ostrog Bible was widely known in
Ukraine,
Russia, and
Belarus, and also abroad. It is registered in the library of
Oxford; its copies were owned by King
Gustavus Adolphus of Sweden, many scientists and the public figures of that time. The
Ostrog Bible was reprinted in
Moscow in 1663.
The significance of the
Ostrog Bible was enormous for
Orthodox education, which had to resist strong Catholic pressure in Ukraine and Belarus." .....