References
http://www.britannica.com/EBchecked/topic/603196/transubstantiation-This provides a basic overview of the meaning of the term and its context in religion as well as its relation to other terms.
http://catholicism.about.com/od/organization/p/The_Papacy.htm- A general overview of what the Papacy is and what the Pope does. Important to have the background of the Pope and his appearance in the painting.
http://www.ewtn.com/faith/teachings/eucha1a.htm- General overview of what Eucharist is and its translation. Also answers questions about the mechanics of the Eucharist.
http://www.history.com/topics/reformation- This provides a general overview of the Protestant Reformation as well as the different reformations in different part of Europe. This is important when studying Lucas Cranach the Elder’s location and how the reformation would have affected his work.
http://www.newadvent.org/cathen/05572c.htm- This provides context for the Eucharist by examining how it fits into Christian lore in relation to other concepts and events in Christian mythology.