books.google.com - The grace and articulate form of the Hancock Center was founded on a bold and exceptionally efficient structural system; the Sears Tower, groundbreaking in its potential for shaping architectural space, introduced Khan's bundled-tube concept for large-scale construction. His designs for long-span roof...http://books.google.com/books/about/Engineering_architecture.html?id=S3l80jXPOewC&utm_source=gb-gplus-shareEngineering architecture
