REMOVE

1. hills (landforms)
2. lines (geometric concept)
3. 1933-1941

WHAT

1. Visual Works (hierarchy n … (1)
2. buildings (structures) (1)
3. drawing (image-making) (1)
4. graphite pencils (1)

More 

WHO

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

WHEN

1. 1933 (1)
2. 1941 (1)