IBM international chess tournament

The IBM international chess tournament was a series of very strong chess tournaments held in the Amsterdam, Netherlands from 1961 to 1981, and was sponsored by IBM. The list of winners of the main group includes five world champions. 
Parallel there was quite often a tournament IBM-B, always with (future or former) strong grandmasters - and local Dutch players to play against foreign titleholders, apart from the major "A" section. By 1963, there were 120 participants in the IBM Amsterdam tournament, broken down to grandmaster group, master group, reserve master group, etc. It was a real festival, connected with the idea to promote (chess) programming by sponsor IBM.