Elisa Morgera, Kati Kulovesi
Edward Elgar, 2016
Buku Teks
Canobbio, Mary M.
Mosby, 1996
Buku Teks
edited by Merlin C. Wittrock; a project of the American Educational Research Association
Macmillan Library Reference USA, 1986
Buku Referensi
Canobbio, Mary M.
Mosby Elsevier, 2006
Buku Referensi
Scarpe, N. V.
Unesco, 1951
Buku Referensi