fbow::VocabularyCreator::create(),fbow::Vocabulary::saveToFile() no reference defined

[luohongk]

When I try to link fbow in cmakefiles, and call VocabularyCreator::create(),fbow::Vocabulary::saveToFile() in the main function but it fails.

There is: set(FBOW_INCLUDE_DIRS "/usr/local/include") in my CMakeList.txt
set(FBOW_LIBS "/usr/local/lib/libfbow.so"). target_link_libraries( main ${FBOW_LIBS}).

The error shows: 'fbow::VocabularyCreator::create(fbow::Vocabulary&, std::vector<cv::Mat, std::allocatorcv::Mat > const&, std::string const&, fbow:: VocabularyCreator::Params)' undefined reference
feature_training_fbow.cpp:(.text.startup+0xd0b): undefined reference to 'fbow::Vocabulary::saveToFile(std::string const&)'

I want to know why something goes wrong?