REMOVE

1. hills
2. machinery
3. buildings (structures)
4. trucks

WHAT

1. Visual Works (hierarchy n … (1)
2. barns (1)
3. black-and-white film (1)
4. exterior views (1)
5. farmers (1)

More 

WHERE

1. Alberta, Canada (1)

WHO

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

WHEN

1. 1940 (1)
2. 1940 September 8 (1)