REMOVE

1. soil
2. trees
3. courtyards
4. colleges (buildings)

WHAT

1. Visual Works (hierarchy n … (1)
2. branches (plant component … (1)
3. buildings (structures) (1)
4. campuses (1)

More 

WHERE

1. San Francisco, California (1)

WHO

1. Clyfford Still; Still, Cl … (1)
2. Still, Clyfford (1)

WHEN

1. 1970 (1)
2. ca. 1970 (1)