Can not build bgslibrary as a static library

[ 95%] Built target bgslibrary_core
[ 96%] Linking CXX executable bgslibrary
libbgslibrary_core.a(KNN.cpp.o): In function `bgslibrary::algorithms::KNN::process(cv::Mat const&, cv::Mat&, cv::Mat&)':
KNN.cpp:(.text+0x12d8): undefined reference to `cv::createBackgroundSubtractorKNN(int, double, bool)'
libbgslibrary_core.a(MixtureOfGaussianV2.cpp.o): In function `bgslibrary::algorithms::MixtureOfGaussianV2::process(cv::Mat const&, cv::Mat&, cv::Mat&)':
MixtureOfGaussianV2.cpp:(.text+0xea0): undefined reference to `cv::createBackgroundSubtractorMOG2(int, double, bool)'
collect2: error: ld returned 1 exit status
CMakeFiles/bgslibrary.dir/build.make:214: recipe for target 'bgslibrary' failed
make[2]: *** [bgslibrary] Error 1
CMakeFiles/Makefile2:104: recipe for target 'CMakeFiles/bgslibrary.dir/all' failed
make[1]: *** [CMakeFiles/bgslibrary.dir/all] Error 2
Makefile:129: recipe for target 'all' failed
make: *** [all] Error 2