Helzer Middle Ages under the pencil in the book icon for Assignments
You have a handout of reference works.
You may also enter your subject keywords [Middle ages, medieval history, feudalism] into the online catalog for more non-fiction works. Add specific topics on a second line with “and.”
Online Databases

Covers human history from prehistoric times to the beginnings of
the Renaissance.
A general search here covers Brittanica and Compton’s
Encyclopedias as well as access to journals, magazine, and
other websites.
Reliable Web Sites
Feudalism – from Google books http://tinyurl.com/562cpr
Chivalry http://www.medieval-life.net/chivalry.htm
Crusades http://www.fordham.edu/halsall/sbook1k.html
Medieval Society http://history.boisestate.edu/westciv/medsoc/
Hundred Years War http://ehistory.osu.edu/osu/archive/hundredyearswar.cfm
Plague http://www.bbc.co.uk/history/british/middle_ages/black_impact_01.shtml