The common causes for "Undefined symbols for architecture armv7" are.
I had a similar issue last night and the problem was related to the fact that I had dragged a class from the Finder to my project in xCode. The solution was to go the the Build Phases tab and then the Compile Sources and make sure you drag the class to the list.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.