Reliable way to tell whether binary linked to MKL or FFTW

Hello,

As I understand, Intel provides wrappers for FFTW. We have a large code base relying on FFT routines. Part of it uses FFTW, and part of it uses MKL. However, in both cases, we use FFTW interface. These "parts" are stand alone executables. I am curious - can we reliably determine whether an executable has been linked to FFTW or MKL (static linking)? I was thinking maybe something simple, like

nm mybin.a | grep -i 'some_unique_MKL_symbol'

Thanks in advance for any help!