Dyfyniad APA

(1999). Ulrich's International Periodicals Directory. R R Bowker.

Dyfyniad Arddull Chicago

Ulrich's International Periodicals Directory. New Jersey: R R Bowker, 1999.

Dyfyniad MLA

Ulrich's International Periodicals Directory. R R Bowker, 1999.

Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.