The gallery closed its doors in 1971. I could no longer psychologically handle the needs of 12 artists. I cared about all of them, and what was happening with their careers. I'm just not a person who can do that indefinitely. And tax-wise I was concerned because they gallery wasn't making money; it was losing money.

There's a definite connection in terms of objects at hand - dealing with objects or material at hand. Pop art was very much enamored with popular imagery, and popular imagery was of course available and at hand. And land art was also using what was at hand.

I remember very vividly. I was here in New York. Nancy Holt called me and - I feel unhappy thinking about it - she said that Bob Smithson had died. I said, "Oh, Nancy, what will we do without Bob?" He was a very good friend.

I think that Walter De Maria's Lightning Field, Michael Heizer's City, and Charles Ross's work in Star Axis New Mexico , all three will last for a millennium.

The gallery closed its doors in 1971. I could no longer psychologically handle the needs of 12 artists. I cared about all of them, and what was happening with their careers. I'm just not a person who can do that indefinitely. And tax-wise I was concerned because they gallery wasn't making money; it was losing money.

I remember when I went to a gallery in Paris at one point, they had drawings of earthworks set in different places. I asked the person sitting at the gallery desk where these works were - where in France they could be found. She looked at me in horror as if I'd asked something completely insane. She said, "Well, of course, these works don't actually exist. They're concepts."

Making the effort is quite a pleasure in itself.