REMOVE

1. trees
2. automobiles
3. rifles (long guns)
4. geometric patterns
5. atmospheric perspective

WHAT

1. Visual Works (hierarchy n … (1)
2. arbors (1)
3. artists (visual artists) (1)

More 

WHERE

1. Westminster, Maryland (1)

WHO

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

WHEN

1. 1961 (1)
2. 1965 (1)
3. between 1961 - 1965 (1)