Eckholm, Erik P.
W.W. Norton, 1976
Buku Teks SO
Academy Group, 1995
Buku Referensi
edited by Toy Magie
Academy Editions, 1995
Buku Teks SO
Tymieniecka, Anna-Teresa
Springer, 2012
eBooks
Chukovsky, Nikolai
Foreign Languages Publishing House , [Date of publication not identified]
Buku Teks SO