REMOVE

1. mothers
2. workers
3. purple
4. gray
5. children

WHAT

1. black-and-white film (1)
2. branches (plant component … (1)
3. exterior views (1)
4. freight cars (1)
5. houses (1)
6. ladders (1)
7. plants (1)
8. railroads (1)
9. rails (transit system ele … (1)
10. roads (1)
11. scaffolds (1)
12. signs (declatory or adver … (1)
13. sky (1)
14. soil (1)
15. trains (vehicle groupings … (1)
16. trees (1)
17. Visual Works (hierarchy n … (1)
18. wheels (components) (1)
19. windows (1)
20. wrecks (sites) (1)

Less

WHERE

1. New Windsor, Maryland (1)

WHO

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

More 

WHEN

1. 1969 (1)