undefined reference to `_WorkLicence' 이 에러 혹시 아시는 분 있으세요? ㅜ.ㅜ

$ make
g++ -Wall -o TargetProgram main.o CarNumber.o Character.o DigitalInOutProcess.o Global.o Hangul.o LPR.o Running.o XString.o
Character.o:Character.cpp:(.text+0x140bf): undefined reference to `_WorkLicence'
Character.o:Character.cpp:(.text+0x140dd): undefined reference to `_WorkLicence'
Character.o:Character.cpp:(.text+0x140fb): undefined reference to `_WorkLicence'
Character.o:Character.cpp:(.text+0x14119): undefined reference to `_WorkLicence'
Character.o:Character.cpp:(.text+0x14137): undefined reference to `_WorkLicence'
Character.o:Character.cpp:(.text+0x1416b): more undefined references to `_WorkLicence' follow
collect2: ld returned 1 exit status
make: *** [CarRecognition.exe] Error 1

위와 같은 에러가 발생 해요.

이유를 모르겠네요.

참고로 cygwin 환경에서 컴파일 한것 입니다.