| title | ISBN-13 (ISBN-10) | year of publica- tion | other author(s) |
|---|---|---|---|
| El Mundo 21 hispano | 978-0-618-49808-6 (0-618-49808-7) | 2004 | Fabian Samaniego · Nelson Rojas · Francisco X. Alarcon |
| Mundo 21 | 978-0-618-67828-0 (0-618-67828-X) | 2004 | Fabian A. Samaniego · Nelson Rojas · Francisco X. Alarcon |