@Book{OL5198865M,
    title: {Western society and the Church in the Middle Ages},
    author: {R. W. Southern and Richard William Southern and Southern, Richard William and R.W. SOUTHERN},
    publisher: {Penguin Books},
    year: {1970},
    place: {[Harmondsworth, Eng.]},
}

@Book{OL5919427M,
    title: {The crisis of church \& state, 1050-1300.},
    author: {Tierney, Brian.},
    publisher: {Prentice-Hall},
    year: {1964},
    place: {Englewood Cliffs, N.J},
}

@Book{OL9303162M,
    title: {Western Society and the Church in the Middle Ages (Hist of the Church)},
    author: {R. W. Southern and Richard William Southern and Southern, Richard William and R.W. SOUTHERN},
    publisher: {Penguin (Non-Classics)},
    year: {1990},
}

@Book{OL7734753M,
    title: {The Papacy, 10731198},
    author: {I. S. Robinson},
    publisher: {Cambridge University Press},
    year: {1990},
}

@Author{OL2764689A,
    name: {I. S. Robinson},
}