REMOVE

1. sky
2. construction equipment
3. barriers
4. clouds
5. atmospheric perspective

WHAT

1. Visual Works (hierarchy n … (3)
2. automobiles (3)
3. exterior views (3)
4. houses (3)
5. lamps (lighting devices) (3)

More 

WHERE

1. New Windsor, Maryland (3)

WHO

1. Campbell, Sandra L. Still (1)
2. Clyfford Still; Still, Cl … (1)
3. Sandra L. Still Campbell; … (1)
4. Still, Clyfford (1)

Less

WHEN

1. 1966 (2)
2. after 1966 (2)
3. 1969 (1)