DLIB and QT under windows. SVM multiclass training unlinked reference - c++

Question

I am trying to build the example provided by dlib for multiple class SVM training using QT on windows. (the example is available at this link: http://dlib.net/multiclass_classification_ex.cpp.html)
first of all I took the DLIB .lib files from a prebuilt library using MS visual studio, and took the include files and modified the QT .pro file to be as follows.
QT -= gui
CONFIG += c++11 console
CONFIG -= app_bundle
DEFINES += QT_DEPRECATED_WARNINGS
SOURCES += main.cpp
INCLUDEPATH += $$PWD/dlib/include
debug {
LIBS += -L$$PWD/dlib/lib -ldlib_debug_64bit_msvc1900
}
!debug {
LIBS += -L$$PWD/dlib/lib -ldlib_release_64bit_msvc1900
}
when i try building the code i get the following errors:
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::~thread_pool_implementation()'
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::shutdown_pool()'
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::thread_pool_implementation(unsigned long)'
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::num_threads_in_pool() const'
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::num_threads_in_pool() const'
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::find_empty_task_slot() const'
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::make_next_task_id(long)'
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::wait_for_all_tasks() const'
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::is_worker_thread(unsigned long) const'
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::find_empty_task_slot() const'
C:\Users\Administrator\Documents\SVMDlib\main.cpp:-1: error: undefined reference to `dlib::thread_pool_implementation::~thread_pool_implementation()'
collect2.exe:-1: error: error: ld returned 1 exit status
knowing that i tried to run the simple SVM code (provided here: http://dlib.net/svm_ex.cpp.html) it compiled and ran perfectly.
Am I missing a library of some kind? as all the errors are linking error and undefined references?