REMOVE

1. roads
2. freight cars
3. trains (vehicle groupings)
4. plants

WHAT

1. Visual Works (hierarchy n … (1)
2. atmospheric perspective (1)
3. black-and-white film (1)
4. churches (buildings) (1)
5. clouds (1)

More 

WHERE

1. New Windsor, Maryland (1)

WHO

1. Campbell, Sandra L. Still (1)
2. Sandra L. Still Campbell; … (1)

WHEN

1. 1966 (1)
2. after 1966 (1)