Paul, Raymond
WW Norton, 1987
Buku Teks
Trevor-Roper, H.R.
New York Harper & Row 1957
Buku Teks SO
Cambridge University Press , Cambridge : Cambridge University Press
Majalah, Jurnal, Buletin
Tilburg : Drukkerij Henri Bergmans N.V
Majalah, Jurnal, Buletin
Helen Dwight Reid Educational Foundation, {s.a}
Majalah, Jurnal, Buletin