Chapter 1: The Age of Religious Reform, 1490-1648

"How Luther Went Viral," The Economist

This article and accompanying video discuss how Martin Luther’s ideas spread and draw parallels to modern social media.
http://www.economist.com/node/21541719

"Calvinism," "In Our Time" podcast

Host Melvyn Bragg and guests discuss the ideas and impact of John Calvin.
http://www.bbc.co.uk/programmes/b00qvqpz

"Holy Roman Empire," Britannica

Read more about the Holy Roman Empire from the Encyclopedia Britannica.
http://www.britannica.com/place/Holy-Roman-Empire