The Adobe Photoshop CS4 Book for Digital Photographers
Photoshop CS4: The Missing Manual
Photoshop CS4 Channels & Masks One-on-One
Adobe Photoshop CS5 One-on-One
Photoshop CS4 Digital Classroom, (Book and Video Training)
Adobe Photoshop CS4 Classroom in a Book
Adobe Photoshop CS4 for Photographers: The Ultimate Workshop