1) Chihuahuas: Domestic Dogs (2007) by Susan H(einrichs) Gray, a picture-oriented book with simple text, an introduction to the breed for very young children.

2-3) The e-book first issued as Housebreaking Breakthroughs for Your Chihuahua Puppy (2008) was allegedly written by James Kelso. Someone probably noticed belatedly that the repetitive "breaking breakthrough" looked silly, so it was re-issued, still as an e-book, as Potty Training Breakthroughs for Your Chihuahua Puppy (2009), but this time by Edward James. It was perhaps written by a committee and the credit is meaningless. It's available from Amazon as a kindle-book. I wouldn't risk wasting money on it personally, assuming the information in it is as much in need of revision as the title and author.