La tierra y la importancia del agua

Before there was the U.S. Constitution, there were the Articles of Confederation. Readers discover the story behind the first written constitution of the United States—from the factors that inspired its creation to the reasons why it was replaced. The detailed main text is enhanced by informative sidebars and graphic organizers. Historical images, including relevant primary sources, allow readers to immerse themselves in this historical period. Readers are given the chance to thoroughly examine elements of the original document, making them feel like true historians. They’re sure to enjoy ...

Esta cuarta edición expone los fundamentos de las señales y sistemas discretos en el tiempo y procesamiento digital de señales. Este texto es adecuado para estudiantes de Ingeniería eléctrica, ingeniería informática y Ciencia de la computación.

Life on Earth depends on carbon. In fact, about 18.5 percent of a human body's mass is carbon. How carbon is taking in and given off through animals' breathing, the burning of fossil fuels, and more can be shown in the model known as the carbon cycle. Though this concept can be confusing, all readers have a chance to understand this concept through the text and simple diagrams in this book. Both struggling readers and those looking for review can find the most important components and vocabulary of the carbon cycle in low-level, accessible text.

November 1940. A circus parade walks through the streets of Warsaw, waving a flag and singing. They are 160 Jewish children, forced by the Nazis to leave their beloved orphanage. It's a sad occasion, but led by Doctor Korczak, their inspirational director, the children are defiantly joyful. Their new home is in the ghetto, a prison for Jews. Two years later they board the train that will carry them away to the death camps. Offered his freedom, Doctor Korczak refuses to abandon the children and proudly joins them on their last journey. This profoundly moving illustrated book is based on the...