Conflict of Investitures
Article from the Catholic Encyclopedia.
Empire and Papacy
An introduction and collection of sources from the Medieval Sourcebook on the relationship between the Pope and the Holy Roman Emperor.
The Investiture Conflict
Lecture by Lynn Nelson in the Online Reference Book for Medieval Studies.
The Owl, The Pussycat and the Investiture Controve
A lecture by Lynn Harry Nelson of the University of Kansas.