REMOVE

1. sidewalks
2. sky
3. windows
4. automobiles
5. ladders
6. buildings (structures)

WHAT

1. Visual Works (hierarchy n … (1)
2. atmospheric perspective (1)
3. black-and-white film (1)

More 

WHERE

1. 48 Cooper Square, New Yor … (1)

WHO

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

WHEN

1. 1952 (1)
2. ca. 1952 (1)