Go to every site to gather all you can regarding your own artist background in the Biography sites. Look at the artist's works in the Galleries, and understand the defintion of Impressionism/Post-Impresionism. Keep good notes as they will be used for your Critique of the artist. There are two artist in this site and each one has its own bibliographies, galleries, and definitions.
BIOGRAPHIES OF MARY CASSATT http://sunsite.icm.edu.pl/cjackson/cassatt/cassatt_bio.htm
http://www.ibiblio.org/wm/paint/auth/cassatt/
http://www.artchive.com/artchive/C/cassatt.html
GALLERIES OF MARY CASSATT http://artcyclopedia.com/artists/cassatt_mary.html
http://www.nga.gov/cgi-bin/psearch?Request=S&Name=cassatt&Title=&imageset=1
http://www.mfa.org/collections/search_art.asp?coll_keywords=Cassatt%20Mary&coll_has_images=1
DEFINITIONS OF IMPRESSIONISM/POST-IMPRESSIONISM http://www.ibiblio.org/wm/paint/glo/impressionism/
http://www.artcyclopedia.com/history/post-impressionism.html
BIOGRAPHIES OF HENRI MATISSE http://www.ibiblio.org/wm/paint/auth/matisse/
http://www.artchive.com/artchive/M/matisse.html
http://www.artelino.com/articles/henri_matisse.asp
GALLERIES OF HENRI MATISSE http://www.artcyclopedia.com/artists/matisse_henri.html
http://artchive.com/artchive/M/matisse.html
http://www.nga.gov/cgi-bin/psearch?Request=S&Name=matisse&Title=&imageset=1
http://www.artcyclopedia.com/artists/matisse_henri.html
http://www.hermitagemuseum.org/fcgi-bin/db2www/quickSearch.mac/gallery?selLang=English&tmCond=Matisse+Henri