Just an anecdote about the making of the film. Many years ago I was at the first preview showing of this film with the director, Johan vd Keuken present. Van der Keuken was, at the time of making this film, one of the Netherlands top documentary filmmakers. Boonzager Flaes was (and probably still is) a rather frustrated university lecturer with filmic ambitions.
When the film was first previewed and the opening titles came into view, Johan vd Keuken got the shock of his life to see that Boonzajer Flaes had tried to claim the film for himself. In the opening titles Bonnzajer Flaes had both placed his name as first director and in larger letters than that of vd Keuken. Boonzajer Flaes had in fact assisted vd Keuken in making the film.
On seeing this titling, Johan vd Keuken became extremely irritated and demanded that the titles be changed immediately. This was done and he never worked with Boonzajer Flaes again.