Joan Mitchell - No. 5 (1955)

Joan Mitchell - Untitled (1960)

From Wikipedia: Joan Mitchell (February 12, 1925 - October 30, 1992) was a ‘Second Generation’ Abstract Expressionist painter. Along with Lee Krasner, Grace Hartigan, and Helen Frankenthaler she was one of her era's few female painters to ...gain critical and public acclaim. Her paintings and editioned prints can be seen in major museums and collections across America and Europe.

Another biographical source:

http://www.theartstory.org/artist-mitchell-joan.htm

Fred Mitchell - Little Tom Big Bee (1958)