Error with fftw compile frealign

Hi, Niko ,
I sole the mkl problem , but get a new error message. It looks like is involve with fftw .
I just have fftw-3.3.6 installed , Do you have any idea what cause this error?

gfortran merge_3d.o frealign_v9.a -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -o ../bin/merge_3d.exe
frealign_v9.a(fftw_plans.o): In function `fftw_plans_2d_':
fftw_plans.f:(.text+0x28): undefined reference to `fftwf_plan_dft_r2c_2d'
fftw_plans.f:(.text+0x42): undefined reference to `fftwf_plan_dft_c2r_2d'
frealign_v9.a(fftw_plans.o): In function `fftw_plans_3d_':
fftw_plans.f:(.text+0x7e): undefined reference to `fftwf_plan_dft_r2c_3d'
fftw_plans.f:(.text+0x9a): undefined reference to `fftwf_plan_dft_c2r_3d'
frealign_v9.a(fftw_plans.o): In function `fftw_fwd_':
fftw_plans.f:(.text+0xb9): undefined reference to `fftwf_execute_dft_r2c'
frealign_v9.a(fftw_plans.o): In function `fftw_bwd_':
fftw_plans.f:(.text+0xca): undefined reference to `fftwf_execute_dft_c2r'
collect2: error: ld returned 1 exit status
make: *** [merge_3d] Error 1

Best,
Zhao