Elaine de Kooning - Bull (1958)

From Wikipedia:

Elaine de Kooning (March 12, 1918- February 1, 1989) was an Abstract Expressionist, Figurative Expressionist painter in the post-World War II era and editorial associate for Art News magazine. On December 9, 1943, she married artist Willem de Kooning, who was a highly influential artist in the Abstract Expressionism movement.

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http://en.wikipedia.org/wiki/Elaine_de_Kooning

Joan Mitchell - No. 5 (1955)

Karel Appel - Danse d'espace avant la tempête (1959)

Christiaan Karel Appel (25 April 1921 – 3 May 2006) was a Dutch painter, sculptor, and poet. He started painting at the age of fourteen and studied at the Rijksakademie in Amsterdam in the 1940s. He was one of the founders of the avant-garde movement Cobra in 1948.

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http://en.wikipedia.org/wiki/Karel_Appel

Philip Guston - The Return (1956-1958)

Philip Guston (June 27, 1913 – June 7, 1980) was a notable painter and printmaker in the New York School, which included many of the Abstract expressionists, such as Jackson Pollock and Willem De Kooning. In the late 1960s Guston helped to lead a transition from Abstract expressionism to Neo-expressionism in painting, abandoning the so-called "pure abstraction" of abstract expressionism in favor of more cartoonish renderings of various personal symbols and objects.

Read more here:

http://en.wikipedia.org/wiki/Philip_Guston