"I had to leave some traces. In the beginning, I would give complete instructions to the photographer. In the '70s, people would come to photograph your work and you would just end up with this crazy material that had nothing to do with your work; maybe I'd pick up two or three photographs that were the closest to the idea. This is why when you look at the '70s, you see much less documentation and really bad material. The material will become misleading to what the piece was."