Acapela TTS engine: "Undefined symbols" in XCode for all classes

I'm trying to get started with the Acapela TTS engine for iPhone. I'm using XCode 4 and I've been following these instructions for setup:

http://www.acapela-for-iphone.com/documentation-quick-start-how-to-add-tts-in-your-app

I've added the voice, and added all the necessary files (from the api and license folders) to a group called "TTS", added them to my project's target, and imported them into one of my view controllers in the same manner as the tutorial. However, when I build I get this message:

Undefined symbols for architecture i386:
  "_OBJC_CLASS_$_AcapelaLicense", referenced from:
      objc-class-ref in NavigationViewController.o
  "_OBJC_CLASS_$_AcapelaSpeech", referenced from:
      objc-class-ref in NavigationViewController.o
      objc-class-ref in AcapelaSetup.o
  "_AcapelaVoiceName", referenced from:
      -[AcapelaSetup SetCurrentVoice:] in AcapelaSetup.o
ld: symbol(s) not found for architecture i386
clang: error: linker command failed with exit code 1 (use -v to see invocation)

There are no errors for the files not being found, and when I cmd+click on on the #import statements it takes me to the relevant source code files. So how come XCode thinks the symbols are undefined?

Solution

Did you include the files libBabTTS.a and libMobilityStatic.a to your project?