Villanueva, P. M. (2009). Discovering one world: (Book IV). Books Atbp.
Chicago-čujuhus (17. p.)Villanueva, Perla M. Discovering One World: (Book IV). Mandaluyong City: Books Atbp, 2009.
MLA-čujuhus (9. p.)Villanueva, Perla M. Discovering One World: (Book IV). Books Atbp, 2009.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.