Deyanova, Mariya, author
B`lgarskata Akademiya na Naukite, 1970
Buku Teks
Ivanova, Kalina, author
Izdatelstvo na b'lgarskata akademija na naukite, 1974
Buku Referensi
Zvegintsev, Vladimir Andreyevich, author
Ministerstva Prosveshheniya RSFSR, 1960
Buku Teks
Ileva, Despina Panaiotova, author
Nauka i Izkustvo, 1972
Buku Teks
Ivanova, Vera Fedorovna, author
Leningradskogo Universiteta, 1962
Buku Referensi