Books on the Chinese Exploration of America

I have a particular interest in pre-Columbian contact between Asia and the Americas, and I've written a blog post on the topic:

Secret Maps of the Ancient World

For those of you interested in Chinese exploration of the Americas before Columbus and before Zheng He, here is a list of books on the subject:

The Asiatic Fathers of America

Secret Maps of the Ancient World

Gods from the Far East

Columbus was Chinese

 The Island of Seven Cities: Where the Chinese Settled When They Discovered America

1421: The Year China Discovered America

1434: The Year a Magnificent Chinese Fleet Sailed to Italy and Ignited the Renaissance

Who Discovered America? The Untold History of the Peopling of the Americas

Nu Sun: Asian-American Voyages, 500 B.C.

Although not a book about Chinese exploration of the Americas, When China Ruled the Seas is an excellent book on Zheng He and the Treasure Fleet.