13 October 1925,
The dictator Primo de Rivera banned all school books that were not in Spanish. If the visits made by the Primary Education inspectors were books in Euskera or with “contrarian tendencies to the unity of the country”, they would be ordered to withdraw them. The professor was informed of the opening of the file, of the abolition of half the salary and of the suspension of work.
Source:
Joan Mari Torrealdai, Siege to the Basque Country: Beyond the black book (Vaccine).