15 March 1980,
The books chased by Spanish censorship were put for sale in San Sebastian Street. It was an initiative of editors and booksellers for freedom of expression. At that time they denounced that censorship prohibited many books. To have legal books, books had to be stamped by the ministry, otherwise booksellers could receive fines.
Source:
Sabino Ormazabal, Bidea Objective Group, 500 non-violent actions, another way to tell the story (Manu Robles Arangiz Foundation).