APA

Bowker Company, . (1975). Ulrich's international peridiocals directory. Estados Unidos: Bowker Company.

Chicago

Bowker Company, . 1975. Ulrich's international peridiocals directory. Estados Unidos: Bowker Company.

Harvard

Bowker Company, . (1975). Ulrich's international peridiocals directory. Estados Unidos: Bowker Company.

MLA

Bowker Company, . Ulrich's international peridiocals directory. Estados Unidos: Bowker Company. 1975.