APA

Baltuck N., Baltuck D., . (1999). Keeper of the Crystal. New York: penguin.

Chicago

Baltuck Naomi, Baltuck Deborah, . 1999. Keeper of the Crystal. New York: penguin.

Harvard

Baltuck N., Baltuck D., . (1999). Keeper of the Crystal. New York: penguin.

MLA

Baltuck Naomi, Baltuck Deborah, . Keeper of the Crystal. New York: penguin. 1999.