Michelangelo’s David
https://en.wikipedia.org/wiki/David_(Michelangelo)
Raphael’s Madonna
http://arthistory.about.com/od/famous_paintings/ss/The-Sistine-Madonna-By-Raphael.htm
da Vinci’s Mona Lisa
http://en.wikipedia.org/wiki/Mona_Lisa
Botticelli’s Primavera
http://en.wikipedia.org/wiki/Primavera_(painting)