*[Object-Oriented Programming with Objective-C](http://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/OOP_ObjC/OOP_ObjC.pdf)(PDF)
*[Objective-C Succinctly, Syncfusion](http://www.syncfusion.com/resources/techportal/ebooks/objective-c)(PDF, Kindle) *(Just fill the fields with any values)*
*[How to Think Like a Computer Scientist: Learning with Python, Interactive Edition](http://interactivepython.org/courselib/static/thinkcspy/index.html)