Agujeros negros (Black Holes)

As a young boy, Jos Marti he traveled to the countryside of Cuba and fell in love with the natural beauty of the land. During this trip he also witnessed the cruelties of slavery on sugar plantations. From that moment, Mart began to fight for the abolishment of slavery and for Cuban independence from Spain through his writing. By age seventeen, he was declared an enemy of Spain and was forced to leave his beloved island. Marti traveled the world and eventually settled in New York City. But the longer he stayed away from his homeland, the sicker and weaker he became. On doctor's orders he...

There are many steps in the nitrogen cycle that include difficult concepts and words: denitrification, prokaryotes, ammonia, and more. With the help of this understandable book, even struggling readers will grasp this cycle of nature. Low-level language, fact boxes, and an extended glossary provide readers with essential vocabulary explanations that allow them to further understand each step of the cycle. Full-color diagrams aid readers' comprehension as they move through the cycle from start to finish, and then around again.

Discover That There Are 6000 Different Kinds Of Dragonflies Because They Are Predators, How Their Body Is Made Up, And How They Reproduce.

La vida de san Francisco de Asís es notablemente diferente de las vidas de los santos al uso. Álvaro Pombo, en simpatía con la antigua tradición franciscana, elige en este libro un estilo correspondiente al gran sobresalto intelectual y afectivo que produce el biografiado. Adopta, por eso, el punto de vista y la voz o voces de los primeros hermanos que acompañaron a Francisco. Con una notable mezcla de atrevimiento, seriedad y simpatía profunda, Álvaro Pombo se convierte, al mismo tiempo, en la voz plural, brillante y humilde de aquella primera comunidad franciscana, una docena mal...