Ward, A. W. (1907). "The Later Years of Thirty Years' War". In Ernest Alfred Benians (ed.). The Cambridge modern history. Vol. 4. University Press. OCLC6253478.
Ward, A. W. (1907). "The Later Years of Thirty Years' War". In Ernest Alfred Benians (ed.). The Cambridge modern history. Vol. 4. University Press. OCLC6253478.