Premo, Bianca
Oxford University Press, 2017
eBooks
Cespedes, Guillermo
Secretaria de Educacion, 1976
Buku Teks
Meade, Teresa A.
Wiley-Blackwell, 2010
Buku Teks
Skidmore, Thomas E.
Oxford University Press, 2001
Buku Teks
Skidmore, Thomas E.
Oxford University Press, 1984
Buku Teks