Contents

21 June 2013
Vol 340, Issue 6139

About The Cover

Cover image expansion

COVER View of Beijing and Tianjin, China, from the International Space Station. Though cities have different sizes and characteristics, mathematical theory can relate size and population density to social, spatial, and infrastructural properties. Such modeling provides a view of the nature of cities and may help urban planners determine how cities evolve and whether they have reached their full potential. See pages 1418 and 1438. Image: Image Science and Analysis Laboratory, NASA?Johnson Space Center