1970, with Charles W. Misner, John Archibald Wheeler*Gravitation*.*Black Holes and Space Warps*. 1994

Coordinate free General Relativity.

Space tells matter how to move.
Matter tells space how to curve.

Time is defined so that motion looks simple.

[I found the metaphor of 'bongs of a bell', used to explain 1-forms, less than illuminating.]