Helminen, Marjaana
Wolters Kluwer, 2010
Buku Teks
Paddeu, Federica, 1982-
Cambridge University Press, 2018
Buku Teks SO
edited by Beth A. Simmons and Richard H. Steinberg
Cambridge University Press, 2006
Buku Teks SO
Shaw, Malcolm Nathan, 1947-
Cambridge University Press, 2017
Buku Teks SO
Fenwick, Charles G.
Appleton-Century-Crofts, 1948
Buku Teks SO