Marie Curie
Research web links
Easy:
http://easyscienceforkids.com/all-about-madame-curie/
Medium:
http://sciencewithme.com/learn-about-marie-curie/
http://www.ducksters.com/biography/women_leaders/marie_curie.php
https://www.mariecurie.org.uk/who/our-history/marie-curie-the-scientist
Difficult:
http://www.bbc.co.uk/history/historic_figures/curie_marie.shtml
https://www.livescience.com/38907-marie-curie-facts-biography.html