José Rizal National Centennial Commission,, 1962.
Buku Teks SO
Franklin, Benjamin
Liberal Arts Press, 1949
Buku Teks SO
Runes, Dagobert D.
Philosophical Library, 1959
Buku Referensi
James, William
Penguin Books, Harmondsworth, Middlesex , 1950
Buku Teks SO
George Allen and Unwin, 1956
Buku Teks SO